Practice Kit Question- Need explanation

Sir there 2 question in my practice kit but i really dont know which topic its related to:
A co. has established the following selling price, cost n revenue equation 4 one of its products
Selling price (per unit) = 50 – 0.025
Marginal revenue = 50 – 0.05Q
Total cost per month = 2000 + 15Q
Q represents the number of units produced and sold per month
a) At what selling price will monthly profits be maximised?
b) What would be the monthly profit if the selling price per unit was set at $20
Can u briefly explain me this
I really appreciate your efforts of answering/clearing 100s of doubts each day.????