How do I solve this problem?

Mt. Nittany Property Management Company and Happy Valley Rentals are two different businesses that manage numerous apartments around town. Both companies use the same monthly profit model given by P(x) = -10x2 + 1800x - 20900 where x represents the number of apartments rented in a month and P(x) is in dollars. (a) Assuming Mt. Nittany Property Management Company manages 100 apartments, find the number of apartments they should rent out each month to maximize profits and calculate their maximum monthly profits. Number of apartments = Maximum monthly profit = dollars (b) Assuming Happy Valley Rentals manages 50 apartments, find the number of apartments they should rent out each month to maximize profits and calculate their maximum monthly profits. Number of apartments = Maximum monthly profits = dollars