4. The president of a consulting firm wants to minimize the total number of hours it will take to complete four projects for a new client. Accordingly, she has estimated the time it should take for each of her top consultants -- Charlie, Gerald, Johnny, and Rick -- to complete any of the four projects, as indicated in the table below. Consultant Charlie Gerald Johnny Rick Project (hours) A B 15 16 13 15 15 21 17 19 C 12 16 20 12 D 18 12 15 22 (a) Find the optimal assignment such that the total number of hours is minimized. (Show your table in each step) (b) What is the optimal assignment? What is the total number of hours required by your optimal assignment