Which of the following statements is true regarding Marginal utility?

i. Marginal Utility is the additional satisfaction a consumer gains from consuming one more unit of a good or service.

ii. Marginal utility is an important economic concept because economists use it to determine how much of an item a consumer will buy

iii. Positive marginal utility is when the consumption of an additional item increases the total utility.

iv. Negative marginal utility is when the consumption of an additional item decreases the total utility.