Assume that there are two consumers (C1 and C2) negotiating the distribution of available resources. In order to have a

unique (single-point) Pareto equilibrium:

a. C1 should have concave, and C2 should have convex preferences

b. None of the listed are correct

c. Both C1 and C2 should have convex preferences

d. C1 should have convex, and C2 should have concave preferences