ONLY ANSWER THIS: How is the answer .92 for Part D?

Please Explain Step-by Step. Thank you.

Kelle Carpet and Trim installs carpet in commercial offices. Peter Kelle has been very concerned with the amount of time it took to complete several recent jobs. Some of his workers are very unreliable. A list of activities and their optimistic completion time, the most likely completion time, and the pessimistic completion time (all in days) for a new contract are given in the following table: D Time (days) Time (days) m b Immediate Predecessor(s) a m b Activity G 3 7 1 3 8 6 4 H 4 Activity A B C D E F 8 2 6 11 5 2 Immediate Predecessor(s) A, E F G HI 1 1 6 2 5 3 8 6 15 BD A, E J K 10 13 3 15 7 12 17 11 4 11 This exercise contains only parts b, c, and d. QUESTION D (ONLY): How is it .92? Please Explain. Step by Step. b) Activities on the critical path for the project are C-D-E-F-H-K. The total project completion time is 36.67 days. (Round your response to two decimal places.) d) Referring to the standard normal table, the probability that Kelle Carpet and Trim will finish the project in 40 days or less is 0.92 (Enter as a probability and round your response to two decimal places.)