An orchard grower currently has 200 apple trees, with an average yield of 450 apples per tree...?

An orchard grower currently has 200 apple trees, with an average yield of 450 apples per tree. She estimates that for each additional set of 10 trees the average yield per tree would drop by 15 apples. How many trees will produce the maximum yield of her apple crop? What is the maximum number of apples that would be produced?