Can someone explain this? I do not understand where the contribution per machine hour comes from.

Pepper Corp. produces three products, and currently has a shortage of machine hours since one of its two machines is down. The selling price, costs, and machine time requirements of the three products are as follows: In what order should Pepper Corp prioritize production of its products to maximize profit while the machine is down? A, B, C C, A, B B, C, A C., B, A The contribution margin per machine hour is $2 for A, $4 for B, and $3 for C. Profit will be maximized by prioritizing Product B, then C, then A