Use the two steps for solving a linear programming problem, given in the box on page 606, to solve the problems in Exercises 17–23.

In 1978, a ruling by the Civil Aeronautics Board allowed Federal Express to purchase larger aircraft. Federal Express’s options included 20 Boeing 727s that United Airlines was retiring and/or the French-built Dassault Fanjet Falcon 20. To aid in their decision, executives at Federal Express analyzed the following data:Federal Express was faced with the following constraints:• Hourly operating cost was limited to $35,000.• Total payload had to be at least 672,000 pounds.• Only twenty 727s were available. Given the constraints, how many of each kind of aircraft should Federal Express have purchased to maximize the number of aircraft?

Direct Operating Cost Payload Boeing 727 $1400 per hour 42,000 pounds Falcon 20 $500 per hour 6000 pounds