Astore has two types of animal feed available. type a contains 9 pounds of oats and 3 pounds of corn per bag. type b
contains 2 pounds of oats and 10 pounds of corn per bag. a farmer wants to combine the two types so that the resulting
mixture has at least 57 pounds of oats and at least 75 pounds of corn. the store only has 15 bags of type a feed and 15
bags of type b feed in stock. type a costs $4 per bag, and type b costs $4 per bag. how many bags of each type should the
farmer buy to minimize her cost?