please solve b and c parts

1. Consider a project that has been modeled as in Table 1. Table 1: Activities and Predecessors Activity Immediate Predecessors Duration A B 7 6 3 12 D B.C B.C 14 E F DE 5 a. Draw the PERT/CPM network for this project and determine the project's expected completion time up and its critical path. b. Suppose the standard deviations of the activity durations are of = 2, 0B = 1, ac = 0, op = 2, 0E = 3, and ap = 0. Then please estimate the standard deviation of the overall project's standard deviation ap. c. Suppose for the standard Normal random variable 2, we know Pl-15 ZS +1] 68%. PL- 225 +295%, and PL-3