The current number of coupons being mailed out by a company each week in one region of the country can be represented by the function R(x) = 3x2 + 21x
where x is the number of cities in the region. The number of coupons in a new mailing sent only to preferred customers can be represented by the function
P(x) = 9x.

Which function best describes C(x), the number of coupons that are shipped out in any given week?
A. C(x) = 3x²+ 30x
B. C(x) = 12x² + 21x
C. C(x) = 3x² + 12x
D. C(x) = -6x² + 21x