DoorDash, Inc., headquartered in San Francisco, California, delivers online food orders from restaurants to customers using private vehicles and their drivers, known as Dashers. At any point in time for a given region, DoorDash can offer its drivers available pickups for delivery. The file doordash contains data on the amount of time it will take for each of 15 Dashers to reach the restaurant locations of 10 current food orders.

a. Formulate a linear programming model to minimize the sum of the times of assignments made such that no Dasher is assigned to more than one order and each order must be assigned to exactly one Dasher.

b. Solve the model formulated in part (a). What is the minimum total time? Which Dashers are assigned and which are unassigned?