Consider the project described in problem $3.$ Suppose that the activity times are random

variables with a constant coefficient of variation of $0\mathrm{.}2.($The coefficient of variation is

the ratio $\frac{}{}.)$ Assume that the times given in problem $3$ are the mean activity times.

a$.$ Compute the standard deviation of each of the activity times.

b$.$ Find the mean and the variance of the path with the longest expected completion time.

c$.$ Using the results of part $($b$),$ estimate the probability that the project is completed

within $20$ weeks.

d$.$ Using the results of part $($b$),$ estimate the number of weeks required to complete the

project with probability $85.$

please solve the question $21$