Question

Step by step please!

f(x,y) is a differentiable function with f (20, -100) = (5, -2). Let g(x,y) = f (xy2, 2x2y) and calculate g(5,-2). Let n = (4,2). What is the directional derivative (5, -2)? Use the above to approximate g(4,0) if g(5, -2) = (2, -1).