If the marginal utility per the price of Good A is $2.40, and the marginal utility per the price for Good B is $2.50, what does the utility-maximizing rule tell you to do, if the budget allows it? 
a. Purchase 1 more unit of Good A and compare again.
b. Purchase 1 more unit of Good B and stop. 
c. Purchase 1 more unit of Good A and stop. 
d. Purchase 1 more unit of Good B and compare again.