Exercise 21

Use the Chain Rule to find the indicated partial derivatives. \(z = x^4 + x^2y\), \(x = s + 2t - u\), \(y = stu^2\); find \(\frac{\partial z}{\partial s}\), \(\frac{\partial z}{\partial t}\), \(\frac{\partial z}{\partial u}\) when \(s = 4, t = 2, u = 1\).