If, at a given level of output, marginal social benefit is greater than marginal social costs, then: a) Social surplus will increase if quantity increases, since social costs fall and social benefits rise. b) Social surplus will increase if quantity increases, since social benefits rise by more than social costs rise. c) Social surplus will increase if quantity decreases, since social benefits fall by less than social costs fall. d) Social surplus will increase if quantity decreases, since social benefits rise and social costs fall.