Suppose f is a differentiable function of x and y, and g(r, s) = f(4r - s, s - 6r). Use the table of values below to calculate g (2, 5) and gs(2, 5). f g X (3, 13) 3 4 9 5 (2, 5) 4 3 6 9, (2, 5) = Is(2, 5) =