World Delivery Service (WDS) specializes in the pickup and delivery of packages at homes and businesses throughout the United States and around the world. WDS's fleet trucks leave from local depots and make a number of pickup and delivery stops before returning to the depot. Each such stop requires an average of three minutes of time, not including travel time between locations. Additionally, many of WDS's customers specify a specific time window within which pickups and deliveries may be made. If a WDS truck arrives at a location before the start of its time window, the truck and driver must simply wait until the start of the specified time window to complete the service at that location. If the truck arrives after the close of the specified time window, the customer often allows for pickup and delivery anyway, but sometimes WDS must come back the following day. Either way, arriving late creates problems for both WDS and its customers and is a practice best avoided if at all possible. The file named WDSData.xlsx that accompanies this book contains data describing travel times between 29 customer locations for which a given WDS driver must make pickups and deliveries. It also lists the time windows for each customer within which these pickups and deliveries are to be made. The top priority at WDS is to provide service within the customer-specified time windows and, secondarily, to minimize the travel time of its trucks as fuel consumption is a major expense to the company. Assume the truck leaves its depot at 3:00 p.m. In what order should the WDS truck service these customers?

a. Create a spreadsheet model for this problem, and solve it using Solver's evolutionary engine.

b. In what order should the WDS truck service these customers?

c. How many time windows are violated in the solution you identify?

d. What is the total travel time associated with this solution?