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? "