Please Solve for units and max profit

The total prot P(x) (in thousands of dollars) from a sale ofx thousand units of a new product is given by P(x) = In ( -x3 + 9x2 + 21x+1) (O st 10). a) Find the number of units that should be sold in order to maximize the total prot. b) What is the maximum prot? a) The number of units that should be sold in order to maximize the total prot is :l. (Simplify your answer.)