PERT allows the estimator to include three estimates: optimistic, pessimistic, and most likely, given by the equation Expected Duration = [P + 4(ML) + O]/6. Range is +/- standard deviation = (P-O)/6, where P is the pessimistic estimate, ML is the most likely estimate, and O is the optimistic estimate. Using this method, the correct answers comes out to be 61.67 days and range (+/-Standard Deviation) is 8.00.