Feasible regions?

Question

an appliance manufacturer makes two kinds of refrigerators: model A, which earns R100 profit and model B which earns R120 profit. Each month the manufacturer can produce up to 600 units of model A and 500 units of model B. If there are only enough man hours to produce more than a total of 900 refrigerators per month, how many of each kind should be produced to obtain the maximum profit?

Answer 1

Since you make more on B, make as many B's as possible.

Thus, 500 B's. Total is 900, so 400 A's.

Answer 2

Too early in the morning to solve simultaneous equations.