Find the derivative of f(x) = x3 + 3x2 + 7 at x = -3 using the alternative form of the derivative. If the derivative does not exist, enter DNE. Which of the following options correctly represents f'(-3)?
Options:
A) f'(-3) = 9
B) f'(-3) = -9
C) f'(-3) = 15
D) f'(-3) = -15