CARD, Cleveland Area Rapid Delivery, operates a delivery service in the Cleveland metropolitan area. Most of CARD's business involves rapid delivery of documents and parcels between offices during the business day. CARD promotes its ability to make fast and on-time deliveries anywhere in the metropolitan area. When a customer calls with a delivery request, CARD quotes a guaranteed delivery time. The following network shows the street routes available. The numbers above each arc indicate the travel time in minutes between the two locations.
a. Develop a linear programming model that can be used to find the minimum time required to make a delivery from location 1 to location 6.
b. How long does it take to make a delivery from location 1 to location 6?
c. Assume that it is now 1:00 P.M. CARD just received a request for a pickup at location 1, and the closest CARD courier is 8 minutes away from location 1. If CARD provides a 20% safety margin in guaranteeing a delivery time, what is the guaranteed delivery time if the package picked up at location 1 is to be delivered to location 6?