how do i get these answers?

Using PERT, Adam Munson was able to determine that the expected project completion time for the construction of a pleasure yacht is 24 months, and the project variance is 4 . a) The probability that the project will be completed in 23 months = (round your response to four decimal places). b) The due date that yields a 95% chance of completion = months (round your response to two decimal places)