The answer is maximizing utility.
When Marietta is making her decision she is trying to get the maximum utility for the money that she has. Â
This is an example of the Utility Maximizing Rule. Â (Keep in mind that utility is defined as the total amount of satisfaction a consumer obtains from consuming a product.) Â The utility maximizing rule explains how consumers decide to allocate their money so that the last dollar spent on each product purchased yields the same amount of extra (marginal) utility.