6. Product X is sold for $500 per unit. The total cost of production per year, including capital recovery and a return, is given by the expression TC 5 0.04n3 2 700n 1 50,000 where n is the number of units sold. If TC represents the total of all fi xed and variable costs, determine the following:

a. The value of n that maximizes profi t

b. The maximum profi t for a year

c. The fi xed cost per year