An appliance store sells two types of refrigerators

An appliance store sells two types of refrigerators. Each Cool-It refrigerator sells for $640 and each Polar sells for $740. Up to 330 refrigerators can be stored in the warehouse and new refrigerators are delivered only once a month. It is known that customers will buy at least 80 Cool-Its and at least 100 Polars each month. How many of each brand should the store stock and sell each month to maximize revenues?
A) 95 Cool-Its and 235 Polars B) 80 Cool-Its and 250 Polars
C) 230 Cool-Its and 100 Polars D) 310 Cool-Its and 175 Polars

Solve using artificial variables.
13) Maximize z = 5x1 + 4x2
subject to: x1 + 2x2 = 15
x1 + x2 12
2x1 + x2 30
x1 0, x2 0
A) Maximum is 75 for x1 = 15, x2 = 0 B) Maximum is 63 for x1 = 11, x2 = 2
C) Maximum is 60 for x1 = 0, x2 = 15 D) Maximum is 57 for x1 = 9, x2 = 3