Q4. Find all the second order partial derivatives of the following func- tions f at the given point Xo. (a) fi(z, y) = sin(ry) and xo = (7, 1) (b) f2(z, y) = x2 + 3ry + y3 and xo = (1, 1) (c) fs(z, y, z) = ev and xo = (1, In(2), In(3))