only part b, please explain step by step

Chapter 6 - Case Problem 4 Auto Restoration (AR) buys 15 used automobiles at each of two car auctions each week held in different locations. It then transports the cars to repair shops it contracts with. When they are restored to AR'S specifications, AR sells 10 each to three different used car tots. There are various costs associated with the average purchase and transportation prices from each auction to each repair shop. Also there are transportation costs from the repair shops to the used car lots. AR is concerned with minimizing its total cost given the costs in the table below. 3. Given the costs below, draw a network representation for this problem. Repair Shops SI S2 550 500 600 450 Auction 1 Auction 2 Used Car Lots L2 300 650 L1 250 350 SI S2 1.3 500 450 b. Formulate this problem as a transshipment linear programming model