The total profit P(x) in thousands of dollars from a sale of x thousand units of a new product is given by P(x) = ln (-x^3 + 9x^2 + 21x + 1) (0 less than or equal to x, x less than or equal to 10).
A) Find the number of units that should be sold in order to maximize the total profit.
B) What is the maximum profit?