Donald's Lunch 2

Donald McRonald often has hamburgers for lunch. The total benefit he gets depends on the number of burgers he eats per week. Here is the relationship between burgers per week and total benefit per week:
burgers benefit in dollars
115
222
326
428
529
629

The marginal benefit of the fourth burger is

7 dollars
4 dollars
2 dollars
1 dollar
0 dollars