Suppose that f: R3 + R2 is defined by f(x, y, z) = (x + yz, sin(xyz) +z). (a) Is f differentiable on R3? (b) Compute the Jacobian matrix of f at (x, y, z) = (-1,0,1). (c) Are there any directions in which the directional derivative of f at (-1,0,1) is zero? If so, find them