Need help with this question? The estimated times and immediate predecessors for the activities in a project at Howard Umrah's retinal scanning

company are given in the following table. Assume that the activity times are independent.

This exercise contains only parts $a,b,c,$ and $d.$

a$)$ Based on the activity time estimates, the expected times and variance for each of the activities are $($round your

response to two decimal places$)$:

b$)$ The expected completion time of the project $=$ weeks $($round your response to two decimal places$).$

c$)$ The project variance of completion time $=$ weeks $($round your response to two decimal places$).$

d$)$ If the time to complete the project is normally distributed, then the probability that the project will be finished in $21$

weeks or less $=($enter as a probability and round your response to two decimal places$).$