The average rate of change of a function f between a and b is defined by \(C(x) = \frac { f(b) - f(a) } { b - a } \). If \(f(2) = 6\) and \(f(5) = 15\), what is the average rate of change between 2 and 5?
(A)3 (B)4 (C)5 (D)7 (E)9
A