25 An ambulance driver has three major routes from the hospital base station to the university, to which he makes several trips weekly. The traffic patterns are, however, very complex. Under good conditions, Broad Street is the fastest route. When Broad is congested, one of the other routes, either Drexel Avenue or the expressway, is usually preferable. Over the past two months, the driver has tried each route several times, under different traffic conditions. This information is summarized (in minutes of travel time to work) in the following table:

ROUTE NO CONGESTION MILD CONGESTION SEVERE CONGESTION Broad Street 10 21 30 Drexel Avenue 13 17 23 Expressway 20 21 20 In the past 50 days, the driver has encountered severe traffic congestion 10 days and mild traffic congestion 20 days. Assume that the past 50 days are typical of traffic conditions.

(a) Which route should the driver take? Remember that we want to find the fastest route.

(b) If the ambulance had a traffic scanner to accurately inform the driver of the level of congestion in this part of town, how much time could he potentially save?