concept of diminishing marginal utility

Explain the concept of diminishing marginal utility, and describe the role that it
plays in the utilitarian argument for the redistribution of income.
The following income distribution data are for a country called New Land. Can you
design a tax to redistribute the income to achieve a equal income distribution?
Quintile Percent Share
Lowest 20% 5%
Second quintile 10%
Third quintile 15%
Fourth quintile 30%
Highest 20% 40%