estimate the mean profit per day of service

library(ggthemes)
library(tidyr)
library(hrbrthemes)
library(tidyverse)
library(lattice)
library(magrittr)
library(lubridate)
dta <- read.csv('Visit_TW.csv')
Day<-as.numeric(as.Date(dta$Depature)-as.Date(dta$Arrival))
##單位(天)
str(Day)

##  num [1:96] 1 5 3 10 6 4 8 5 3 6 ...

mean(dta$Expense)/mean(Day)

## [1] 6439.676

##單位(錢/天)
#不知為何每天利潤和廖同學+1之後不相同，理論上答案應該是一致