Pisa Pizza makes home deliveries of pizzas. Pisa usually waits until four pizzas need to be delivered, but it will deliver any pizza that has been out of the oven for 12 minutes. During peak hours,...

Pisa Pizza makes home deliveries of pizzas. Pisa usually waits until four pizzas need to be delivered, but it will deliver any pizza that has been out of the oven for 12 minutes. During peak hours, the former condition usually applies.

 Vince Petralia is one of several college students working as a delivery person for Pisa Pizza. The following network depicts the time between the destinations of the four pizzas he is to deliver at 6:00 P.M. Note that, because of traffic patterns, delivery times between points could depend on the direction traveled.

a. Suppose the time spent at each delivery point (walking to the door and collecting the money) is about three minutes. What is the minimum time it will take Vince to deliver the four pizzas and return to Pisa Pizza?

 b. Suppose the situation in part (a) is representative of a “typical” pizza run for Vince during his shift from 5:00 P.M. to 11:00 P.M. Assume that, on the average, once Vince returns to Pisa Pizza he spends 15 minutes at the store (depositing the money collected from the previous run, waiting for and picking up the pizzas, and studying the map to determine the locations of the next set of deliveries). If he is paid $5 per hour by Pisa Pizza and averages a $1 tip from each pizza delivery, how much can Vince expect to earn in a typical night?