Solve A, B please! thank you

11. Let J(x, y, z) = 1/x + 2/y + 3/2, defined for all z > 0, y > 0, z > 0. (a) Compute f(1, 1, 1) and / (2,2,2). (4 points) (b) Prove that f(Le, ty, tz) = 1-'S(r, y, z) for all ! > 0. (3 points)