quick and concise response please. thank you

(a) Determine if the following limit exists; if yes, find the limit. lim yr3 (z,y)-(0.0) + y2 (b) Let F(r, y, z) = z y+ resty. Assume that the equation F(r, y, z) = 0 defines z as a function of r and y. Find 2 and # at P(1, -1, 1)