Critical Path Method Problem

The R&D department is planning to bid on a large project for the development of a new communications

system for commercial planes. The accompanying table shows the activities, times, and sequences required:

Figure $1$: Time Estimates

a$.$ Draw the network diagram.

b$.$ What is the critical path?

c$.$ Suppose you want to shorten the completion time as much as possible, and you have the option of

shortening any or all of B$,$ C$,$ D$,$ and G each one week. Which would you shorten?

d$.$ What is the new critical path and earliest completion time?