Given f(x) = 4sqrt(x) - 8, find f'(x) using the limit definition of the derivative.

a) Limit as h approaches 0 of (f(x+h) - f(x)) / h
b) Limit as x approaches 0 of (f(x+h) - f(x)) / h
c) Limit as h approaches infinity of (f(x+h) - f(x)) / h
d) Limit as x approaches infinity of (f(x+h) - f(x)) / h