Suppose three types of planes (Piper Cubs, DC-10s, and 707s) use an airport. A Piper Cub requires a 100-yd runway, a DC-10 requires a 150-yd runway, and a 707 requires a 400-

yd runway. Suppose the cost (in dollars) of maintaining a runway for one year is equal to the length of the runway. Because 707s land at the airport, the airport will have a 400-yd runway. For simplicity, suppose that each year only one plane of each type lands at the airport.

How much of the $400 annual maintenance cost should be charged to each plane?