please solve all parts and show steps

Problem 4: Each year, Data Corporal produces as many as 400 computers in Boston and 300 computers in Raleigh. Los Angeles customers must receive 400 computers, and 300 computers must be supplied to Austin customers. Producing a computer costs $800 in Boston and $900 in Raleigh. Computers are transported by plane and may be sent through Chicago. The costs of sending a computer between pairs of cities are shown in the following table: To ($) From Chicago Austin Los Angeles Boston 80 220 280 Raleigh 100 140 170 Chicago 49 50 Part a: Formulate a minimum-cost flow problem that can be used to minimize the total cost of meeting Data Corporal's annual demand. For this problem, you should provide a drawing of the minimum-cost flow network. Explain in words what nodes and arcs represent, and label nodes and arcs with all relevant data. Part b: Repeat part a if at most 200 units can be shipped through Chicago. (Hint: Add an additional node and arc to your network from part a.)