Figure: Marginal Benefits and Marginal Costs

Figure: Marginal Benefits and Marginal Costs
(Figure: Marginal Benefits and Marginal Costs) Look at the figure Marginal Benefits and Marginal Costs.As shown, more time spent studying economics adds points to economics scores but (MB) subtracts points from accounting scores (MC).When Claudia studies economics for 4 hours, the marginal benefit is points; when Claudia studies for 6 hours, the marginal benefit is
________ points.
A.20; 10
B.30; 10
C.20; 0
D.20; 30