A marginal rate of substitution formula tells us: Select one: a the rate at which the consumer is willing to exchange one good for another, given the level of utility O b. the rate at which the consumer is willing to exchange one good for another, given the prices of the goods. Oc the rate at which the consumer is willing to exchange one good for another, given the amounts consumed. O d. the rate at which the consumer is willing to exchange one good for another, given the consumer's income