Alan Is Sitting in a Bar Drinking Beers That Cost

Alan is sitting in a bar drinking beers that cost $1 each.According to the economic decision rule, Alan will quit drinking when the marginal:

A) benefit to him of an additional beer is less than$1....
B) cost to him of an additional beer is less than the marginal benefit.
C) cost remains at$1....
D) benefit to him of an additional beer is greater than$1....