Casey Consumes Two Goods,hamburgers and Ice Cream Sandwiches

Multiple Choice

Casey consumes two goods,hamburgers and ice cream sandwiches.He has maximized his utility given his income.Ice cream sandwiches costs $2,and he consumes them to the point where the marginal utility he receives is 6.Hamburgers cost $4,and the relationship between the marginal utility that Casey gets from eating hamburgers and the number he eats per month is as follows:
How many hamburgers does Casey buy each month?

A) 1
B) 2
C) 3
D) 4