10. Classify each of the functions listed below as one of the following: convex; con- cave; both convex and concave; neither convex nor concave. Explain Why. (a) f(x) = Vx, x e R and x 2 0; (b) f(x) = et, x ER; (c) f(x) = HM, TER; (d) f(x) = 2 - 3.142 + 2.3, x E R2; (e) f(x) = 2+23+213 -142 - 1203 - 13, T E R3