Delta Airlines flies planes on the following route: L.A. - Houston N.Y. Miami L.A. The length in miles of each segment of this trip is as follows: L.A. Houston, 1500 miles; Houston N.Y. 1700 Miami, 1300 miles; Miami L.A., 2700 miles. At each stop, the plane may purchase up to 10,000 gallons of fuel. The price of fuel at each city is as follows: L.A., $ 8.8; Houston, $1.5; N.Y., $10.5; Miami, $9.5. The plane's fuel tank can hold at most 12,000 gallons. To allow for the possibility of circling over a landing site, it is required that the ending fuel level for each leg of the flight be at least 600 gallons. The number of gallons used per mile on each leg of the flight is Average fuel level on leg of flight 1+ 2000 To simplify matters, assume that the average fuel level on any leg of the flight is calculated as follows Fuel level at start of leg + Fuel level at end of leg) 2 Help Delta minimize the fuel costs incurred in completing the schedule. a) Propose an extended formulation for this problem instance b) Proposed a generalized formulation for this problem. c) Solve the problem instance in AMPL using the proposed generalized formulation.