Suppose you are visiting the local Big Y supermarket to purchase groceries. At the grocery, you see an advertisement for a store rewards card. The card offers gasoline discounts that are tied to the amount of money that a consumer spends at the store. The advertisement explains that the discounts accrue after a minimum purchase of $50. You decide to sign up for the card, in spite of the fact that you had only planned to buy $47 worth of groceries. Why is this decision rational? Explain, using a fundamental principle of economics, why you would make this decision.

Develop a response that includes examples and evidence to support your ideas, and which clearly communicates the required message to your audience. Organize your response in a clear and logical manner as appropriate for the genre of writing. Use well-structured sentences, audience-appropriate language, and correct conventions of standard American English.