A hospital's revenue (in millions of dollars) is projected to be R(x) = 9x2 + 7x + 81 and its costs (in millions of dollars) are projected to be
C(x) = -2x2 - 10x - 14 where x represents the number of years into the future.
a. Create the profit function for the hospital.
b. What is the average rate of change in the profit from year 3 to year 5?