7. A business has purchased land and plans to build apartment buildings on that land. Due to the size of the land, the company can build any number of apartments up to a maximum of 500 apartments. From past experience, the company knows that the maintenance cost of a complex with x apartments will be: C(x) = 4000 + 14x - 0.04x2 How many apartments should be on the land if the company wishes to minimize the maintenance costs