The new director of special events at a large university has decided to completely revamp the graduation ceremonies. Toward that end, a precedence network of the major activities has been developed. The network has five paths with expected durations and variances as shown in the following table. Graduation day is 16 full weeks from now. Assuming that the project begins now, what is the probability that the project will be completed before:
a. Graduation day?
b. The end of week 15?
c. Tire end of week 13?