#POSTEST

eks <- function(x, lambda){lambda*exp((-1)*lambda*x)}
eks(4, 1/6)          
## [1] 0.08556952
cdfexp <- function(x, lambda = 0.05) {
  pdf <- function(t) {
    lambda * exp(-lambda * t)
  }
  hasil <- integrate(pdf, lower = 0, upper = x)
  return(hasil$value)
}
cdfexp(4, 1/6)      
## [1] 0.4865829