A principal was buying T-shirts for his school's chess club and found that the total cost in dollars could be found by the function f(x) = 9x + 5, where x is the number of
members in the club. If there are at least 9 members on the team but not more than
13, then which of the following statements describes the function?

A. The value of x must be a whole number between 0 and 122 and the value of f(x)
must be a whole number between 0 and 13.

B. The value of x must be a whole number between 9 and 13 and the value of f(x) must
be a whole number between 86 and 122.

C. The values of x and f(x) must both be whole numbers between 86 and 122.

D. The values of x and f(x) must both be whole numbers between 9 and 13.