JAMB - Economics (2008 - No. 9)
As long as marginal utility is positive, total utility must be
negative
increasing
zero
decreasing
Forklaring
When marginal utility diminishes but stays positive, then total utility increases at a decreasing rate as it is the summation of all marginal utilities.
This is because positive marginal utility occurs when the consumption of an additional item increases the total utility. Hence whenever marginal utility is positive, total utility increases.