A project manager for Durable Construction Co. is about to build a house involving the following six activities: DURATION ESTIMATES (days) ACTIVITY PRECEDES OPTIMISTIC MOST LIKELY PESSIMISTIC Start A B AB CD D F F End 44 45 42 31 27 58 50 60 45 40 36 70 56 75 48 49 39 82 F What is the estimated slack time for the path B-D-F? Select one: O a. 40 days Ob 50 days Oc 30 days Od 0 days O e 100 days