SLO 2  When Jane eats two slices of pizza, her total utility…

SLO 2  When Jane eats two slices of pizza, her total utility is 80 units.  When she eats three slices of pizza, her total utility is 120 units.  When she eats four slices of pizza, her total utility is 140 units.  What is the marginal utility of the fourth slice of pizza?