Problem Set 7 Show your steps clearly. 1. Determine whether each function is convex, concave or neither. a. f(x) = 82x + 3c4 b. f(x,y) =x3+3xy+y2 2. Find the values of a, b, and c such that f(x,y) = ax2 + bxy + cyz is a concave function 3. Use the following function to construct a convex set z=x2+ey 4. By drawing sketches, decide if the sets {(35, y) E R2 I y 5 x2} are convex or not