2 (a) If u= x¹y+y²z³, where x = rset, y = rs²e-¹ and z = r² sin t, find the value of = du Əs when r = 2, s =

1, t = 0. [5 marks] (b) Suppose that over a certain region of space the potential is given by (x, y, z) = x sin(yz). Find the directional derivative of the potential at the point P (1,3,0) in the direction of the vector v=i+2j - k. [5 marks]