Find fx (3, 4) and fy (3, 4) given that f ( x, y) = - y y- + X a) Ofx (3, 4) = - 13 13 361 , fy (3, 4) = 361 b) Ofx ( 3, 4) = 13 4 361 , fy (3, 4 ) = - 361 c) Ofx (3, 4) = - 4 361 , fy (3, 4) = 4 361 d) Ofx (3, 4) = - 4 13 361 ' fy (3, 4) = 361 e) Ofx (3, 4) = 28 , fy (3, 4) = 91 361 361 f) O None of these