what is D?

Using PERT Adom Munson was able to determine that the expected project completion time for the construction of a ploasuro yacht is 21 months, and the project variance is 4 a) The probability that the project will be completed in 17 months -0.0228 (round your response to four decimal places). b) The probability that the project will be completed in 20 months = 0.3085 (round your response to your dooie plocos). c) The probability that the project will be completed in 23 months = 0.8413 (round your response to four decimal places). c) The probability that the project will be completed in 25 months = (round your response to four decimal places)