A manufacturer produces three different devices (device A, B and C) at two manufacturing facilities (the San Francisco plant and the New Orleans plant). Each day the San Francisco plant can produce 109 units of device. A, 105 units of device B, and 188 units of device C. at the cost of $3,450. Each day the New Orleans plant can produce 218 units at device A, 315 units of device B, and 282 units of device C at a cost of $4,270. An order for 8,720 units of device A, 9,135 units of device B, and 12,690 units of device C is received. Find the number of days that each plant should operate to meet the orders placed for the three devices at a minimum cost to the manufacturer. Show all the necessary steps needed to solve this problem. You may use your calculator's graphing functions to help solve this problem. Your final answer should be in the form of a sentence.