An icicle drips at a rate that can be represented by the function f(x) = −x2 + 8x − 7, 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 = −1 and x = 7
B) x = 1 and x = 7
C) x = 1 and x = −7
D) x = −1 and x = −7