Let z = f(x, y), x = x(u, v), y = y(u, v) and x(1, 2) = 4, y(1, 2) = 3, calculate the partial derivative in terms of some of the numbers a, b, c, d, m, n, p, q. fx(1, 2) = a fy(1, 2) = c xu(1, 2) = m yu(1, 2) = p fx(4, 3) = b fy(4, 3) = d xv(1, 2) = n yv(1, 2) = qzu(3,4)=