Elk Grove produces three products: A, B and C. A machine is used to produce products. The contribution margins, sale demands and time on the machine(in minutes) are as follows:

DemandCMTime on machine

A120205

B803610

C1005015

There are 2400 minutes available on the machine during the week. How many units should be produced and sold to maximize the weekly contribution

why the answer is?

120

80

66

can someone explain?