The functions $f(x) = x^{-4}$ and $g(x) = 4^{-x}$ both approach zero as $x \to \infty$. Which function approaches zero faster? Support your conclusion numerically.

A. $f(x) = x^{-4}$ approaches zero faster.
B. $g(x) = 4^{-x}$ approaches zero faster.
C. It cannot be determined.