(a) Formulate a minimum cost network flow problem that could be used to minimize the transport costs in meeting the oil demands of Los Angeles and New York. (b) (take home) Assume that before being shipped to Los Angeles or New York, all oil produced at the wells must be refined at either Galveston or Mobile. To refine 1,000 barrels of oil costs $12 at Mobile and $10 at Galveston. Assuming that both Mobile and Galveston have infinite refinery capacity, formulate a minimum cost network flow problem to minimize the daily cost of transporting and refining the oil requirements of Los Angeles and New York