1) Create the vectors

#x,y,z
x<- c (5, 10, 15, 20, 25, 30)
y<- c (-1, NA, 75, 3, 5, 8)
z<- c (5)

2) Multiply

#multiplication by the z vector
x*z
## [1]  25  50  75 100 125 150
y*z
## [1]  -5  NA 375  15  25  40
#creating new objects
p<- c (25, 50, 75, 100, 125, 150)
q<- c (-5, NA, 375, 15, 25, 40)

#printing new vectors
p
## [1]  25  50  75 100 125 150
q
## [1]  -5  NA 375  15  25  40

3) Replace the missing element

#replacing the missing element of y vector
y<- c (-1, NA, 75, 3, 5, 8)
y<-ifelse(test = is.na(y)==T, yes =  2.5, no =y)

y
## [1] -1.0  2.5 75.0  3.0  5.0  8.0
#replacing the missing element of q vector (y vector after multiplying by z)
q<- c (-5, NA, 375, 15, 25, 40)
q<-ifelse(test = is.na(q)==T, yes =  2.5, no =q)

q
## [1]  -5.0   2.5 375.0  15.0  25.0  40.0

4) PRB Data

## Parsed with column specification:
## cols(
##   .default = col_integer(),
##   Country = col_character(),
##   Continent = col_character(),
##   Region = col_character(),
##   Population. = col_double(),
##   Rate.of.natural.increase = col_double(),
##   ProjectedPopMid2025 = col_double(),
##   ProjectedPopMid2050 = col_double(),
##   IMR = col_double(),
##   TFR = col_double(),
##   PercPop1549HIVAIDS2001 = col_double(),
##   PercPop1549HIVAIDS2007 = col_double(),
##   PercPpUnderNourished0204 = col_double(),
##   PopDensPerSqMile = col_double()
## )
## See spec(...) for full column specifications.
#4.1firt 10 country names
head(prb$Country, 10)
##  [1] "Afghanistan"         "Albania"             "Algeria"            
##  [4] "Andorra"             "Angola"              "Antigua and Barbuda"
##  [7] "Argentina"           "Armenia"             "Australia"          
## [10] "Austria"
#4.2how many countries
##1
summary(prb$Country)
##    Length     Class      Mode 
##       209 character character
##2 
list(prb$Country)
## [[1]]
##   [1] "Afghanistan"                    "Albania"                       
##   [3] "Algeria"                        "Andorra"                       
##   [5] "Angola"                         "Antigua and Barbuda"           
##   [7] "Argentina"                      "Armenia"                       
##   [9] "Australia"                      "Austria"                       
##  [11] "Azerbaijan"                     "Bahamas"                       
##  [13] "Bahrain"                        "Bangladesh"                    
##  [15] "Barbados"                       "Belarus"                       
##  [17] "Belgium"                        "Belize"                        
##  [19] "Benin"                          "Bhutan"                        
##  [21] "Bolivia"                        "Bosnia-Herzegovina"            
##  [23] "Botswana"                       "Brazil"                        
##  [25] "Brunei"                         "Bulgaria"                      
##  [27] "Burkina Faso"                   "Burundi"                       
##  [29] "Cambodia"                       "Cameroon"                      
##  [31] "Canada"                         "Cape Verde"                    
##  [33] "Central African Republic"       "Chad"                          
##  [35] "Channel Islands"                "Chile"                         
##  [37] "China"                          "China Hong Kong SARe"          
##  [39] "China Macao SARe"               "Colombia"                      
##  [41] "Comoros"                        "Congo"                         
##  [43] "Congo Dem. Rep."                "Costa Rica"                    
##  [45] "C<U+FFFD>te d'Ivoire"           "Croatia"                       
##  [47] "Cuba"                           "Cyprus"                        
##  [49] "Czech Republic"                 "Denmark"                       
##  [51] "Djibouti"                       "Dominica"                      
##  [53] "Dominican Republic"             "Ecuador"                       
##  [55] "Egypt"                          "El Salvador"                   
##  [57] "Equatorial Guinea"              "Eritrea"                       
##  [59] "Estonia"                        "Ethiopia"                      
##  [61] "Federated States of Micronesia" "Fiji"                          
##  [63] "Finland"                        "France"                        
##  [65] "French Guiana"                  "French Polynesia"              
##  [67] "Gabon"                          "Gambia"                        
##  [69] "Georgia"                        "Germany"                       
##  [71] "Ghana"                          "Greece"                        
##  [73] "Grenada"                        "Guadeloupe"                    
##  [75] "Guam"                           "Guatemala"                     
##  [77] "Guinea"                         "Guinea-Bissau"                 
##  [79] "Guyana"                         "Haiti"                         
##  [81] "Honduras"                       "Hungary"                       
##  [83] "Iceland"                        "India"                         
##  [85] "Indonesia"                      "Iran"                          
##  [87] "Iraq"                           "Ireland"                       
##  [89] "Israel"                         "Italy"                         
##  [91] "Jamaica"                        "Japan"                         
##  [93] "Jordan"                         "Kazakhstan"                    
##  [95] "Kenya"                          "Kiribati"                      
##  [97] "Korea North"                    "Korea South"                   
##  [99] "Kosovof"                        "Kuwait"                        
## [101] "Kyrgyzstan"                     "Laos"                          
## [103] "Latvia"                         "Lebanon"                       
## [105] "Lesotho"                        "Liberia"                       
## [107] "Libya"                          "Liechtenstein"                 
## [109] "Lithuania"                      "Luxembourg"                    
## [111] "Macedoniag"                     "Madagascar"                    
## [113] "Malawi"                         "Malaysia"                      
## [115] "Maldives"                       "Mali"                          
## [117] "Malta"                          "Marshall Islands"              
## [119] "Martinique"                     "Mauritania"                    
## [121] "Mauritius"                      "Mayotte"                       
## [123] "Mexico"                         "Moldova"                       
## [125] "Monaco"                         "Mongolia"                      
## [127] "Montenegro"                     "Morocco"                       
## [129] "Mozambique"                     "Myanmar"                       
## [131] "Namibia"                        "Nauru"                         
## [133] "Nepal"                          "Netherlands"                   
## [135] "Netherlands Antilles"           "New Caledonia"                 
## [137] "New Zealand"                    "Nicaragua"                     
## [139] "Niger"                          "Nigeria"                       
## [141] "Norway"                         "Oman"                          
## [143] "Pakistan"                       "Palau"                         
## [145] "Palestinian Territory"          "Papua New Guinea"              
## [147] "Paraguay"                       "Peru"                          
## [149] "Philippines"                    "Poland"                        
## [151] "Portugal"                       "Puerto Rico"                   
## [153] "Qatar"                          "Reunion"                       
## [155] "Romania"                        "Russia"                        
## [157] "Rwanda"                         "Saint Lucia"                   
## [159] "Samoa"                          "San Marino"                    
## [161] "Sao Tome and Principe"          "Saudi Arabia"                  
## [163] "Senegal"                        "Serbia"                        
## [165] "Seychelles"                     "Sierra Leone"                  
## [167] "Singapore"                      "Slovakia"                      
## [169] "Slovenia"                       "Solomon Islands"               
## [171] "Somalia"                        "Spain"                         
## [173] "Sri Lanka"                      "St. Kitts-Nevis"               
## [175] "St. Vincent & the Grenadines"   "Sudan"                         
## [177] "Suriname"                       "Swaziland"                     
## [179] "Switzerland"                    "Syria"                         
## [181] "Taiwan"                         "Tajikistan"                    
## [183] "Tanzania"                       "Thailand"                      
## [185] "Timor-Leste"                    "Togo"                          
## [187] "Tonga"                          "Trinidad and Tobago"           
## [189] "Tunisia"                        "Turkey"                        
## [191] "Turkmenistan"                   "Tuvalu"                        
## [193] "Uganda"                         "Ukraine"                       
## [195] "United Arab Emirates"           "United Kingdom"                
## [197] "United States"                  "Uruguay"                       
## [199] "Uzbekistan"                     "Vanuatu"                       
## [201] "Venezuela"                      "Vietnam"                       
## [203] "Western Sahara"                 "Yemen"                         
## [205] "Zambia"                         "Zimbabwe"                      
## [207] "Panama"                         "South Africa"                  
## [209] "Sweden"
##3
str(prb$e0Total)
##  int [1:209] 43 75 72 NA 43 73 75 71 81 80 ...
#4.3missing countries
prb$e0Total[is.na(prb$e0Total)]
## [1] NA NA
#4.4which countries are missing
list (prb$Country[is.na(prb$e0Total)])
## [[1]]
## [1] "Andorra" "Monaco"