this is actually Operation Research. Answer all plis in clear thankyou

The Farmer's American Bank of Leesburg is planning to install a new computerized accounts system. Bank management has determined the activities required to complete the project, the precedence relationships of the activities, and activity time estimates, as shown in the following table: Activity Predecessor Time Estimates (weeks) a b Activity m 5 3 b d 23 Activity Description Position recruiting System development System training Equipment training Manual system test Preliminary system changeover Computer-personnel interface Equipment modification Equipment testing System debugging and installation Equipment changeover f - a b, c b.c de de h fig 5 1 1 3 1 1 2 5 8 12 7 8 1 4 6 2.5 1 2 8 FN-vous T j K 11 Determine the expected project completion time and variance and determine the probability that the project will be completed in 40 weeks or less