Finding the Average Cost Function

"Biologists want to set up a station to test alligators in the lake for West Nile Virus. Suppose that the costs for such a station are $2,500 for setup costs and $3.00 to administer each test.
a. As the number of animals tested increases, what happens to the average cost to test the animals? Would the average cost ever fall below $3.00?
b. How many animals should be tested for the average cost to be $5.00 per animal?
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