When identical units of an item are purchased at different costs, a. an inventory cost flow method must be used under a perpetual inventory system only. b. an inventory cost flow method must be used under both a perpetual and a periodic inventory system. c. an inventory cost flow method is not used under either a perpetual or a periodic inventory system. d. an inventory cost flow method must be used under a periodic inventory system only?

What is the difference between total utility and marginal utility? a. marginal utility is subject to the law of diminishing marginal utility while total utility is not. b. total utility represents the consumer optimum while marginal utility gives the total utility per dollar spent on the last unit. c. total utility is the total amount of satisfaction derived from consuming a certain amount of a good while marginal utility is the additional satisfaction gained from consuming an additional unit of the good. d. marginal utility represents the consumer optimum while total utility gives the total utility per dollar spent on the last unit.