Please help with practice problems 4 and 5.

4) Find the maximum and minimum values attained by f (in, y, z) = wyz on the unit ball 2:2 + y2 + :52 g 1. 5) '2 Letf (m) = H if (m) a (o, 0) and f (o, o) = o. {a} If (:c,y) 75 (0, 0), calculate and 5f Ba: By (b) Show that ::,(0 0): 3f (0,0) = 0. W2 (c ) Show that Lay as: (0 0): a: 6y \"(0 U): 1 {d} What went wrong? Why are the mixed partials not equal