3. Let \(f(x)=x-4\), \(g(x)=\sqrt{x}\), and \(h(x)=x^{2}\). Find each composition and state its domain.

a) \(f\circ{g}\)

b) \(g\circ{f}\)

c) \(f\circ{h}\)

d) \(g\circ{f}\circ{h}\)