Answer:
mary
Step-by-step explanation:
A rational consumer would consume up to the point that marginal benefit equal marginal cost
Mary paid $20. this means that she places a value of $20 on the meal.
Paul paid $10. this means that he places a value of $10 on the meal
The value Mary places is 20, so she places a higher value and she would consume the most
Peter enters free and thus there is no marginal cost attached to this decision. He should consume the least