An icicle drips at a rate that can be represented by the function f(x)= - x^2 + 11x - 18, where 0 < x < 10 and x is the number of hours after the sun has risen. When f(x) is a negative number the icicle is not dripping. Determine the values when the icicle starts and stops dripping.

A.) x = 2 and x = 9

B.) x = -2 and x = 9

C.) x = 2 and x = -9

D.) x = -2 and x = -9