A gym charges 600 dollars per year to join, and the gym expects they will have 3,000 members when charging this fee. The gym plans to increase its yearly membership fee in increments of 20 dollars. But, for each 20 dollar increase, they expect to have 30 less members. Let x be the number of increases and f(x) be the amount of revenue. The function is f(x)=(600+20x)(3000−30x).
What total membership fee would result in the highest possible total revenue for the gym?
A
The membership fee will be $100 per year.

B
The membership fee will be $760 per year.

C
The membership fee will be $1,300 per year.

D
The membership fee will be $1,950 per year.