melanie works 50 hours each week and earns an hourly wage $w. she can work another hour, or she can enjoy an hour of leisure with her children. the opportunity cost of an hour of leisure is equal to a the hourly wage $w. b the marginal utility of leisure. c the marginal utility of leisure divided by the wage $w. d total earnings of 50 hours multiplied by $w per hour. e the utility she gains from spending time with her children.