Question: Dove corporation in Austin, TX, has just developed a new dishwashing liquid and is preparing for a national television promotional campaign. The firm has decided to schedule a series of one-minute commercials during the peak housewife audience viewing hours of 1:00 to 5:00 P.M, To reach the widest possible audience, Dove wants to schedule one commercial on each of four networks and have one commercial appear during each of the four one-hour time blocks. The appropriate ratings for each hour, representing the number of viewers (in 1,000s), are presented in the accompanying table:

Solve this special assignment problem to determine which network should be scheduled during each hour order to provide the maximum audience exposure. What is number of to be reached?