If f(x)=x2−4f(x) = x^2 - 4f(x)=x2−4 and g(x)=xg(x) = \sqrt{x}g(x)=x, find the domain of (g∘f)(x)(g \circ f)(x)(g∘f)(x).
x \ge 2
x \ge 0
x \ge 2 \text{ or } x \le -2
x \ge 4