When the marginal utility of a commodity is zero the total utility is

When the marginal utility of a commodity is zero, the total utility is at its maximum. The concept of marginal utility states that the additional satisfaction or benefit a consumer derives from consuming an additional unit of a good or service decreases as they consume more of that good or service. Therefore, when the marginal utility of a commodity is zero, the consumer has consumed an amount of the commodity where the additional satisfaction they get from consuming an extra unit is negligible or zero. This means that the total utility that the consumer derives from consuming that commodity is at its highest point because any additional units would provide no additional benefit or satisfaction.