When comparing the prices of two different pairs of shoes, money serves as a unit of account. Let's go through the primary functions of money to understand why:
1. Medium of Exchange: Money is used as an intermediary in trade to avoid the complications of a barter system. For example, if you wanted to buy a pair of shoes, you would use money to do so instead of trading goods or services directly.
2. Store of Value: Money can hold its value over time, allowing individuals to save or invest their earnings. For instance, you can save money today and use it in the future to purchase shoes or other goods.
3. Unit of Account: This function of money provides a standard numerical unit of measurement of market value. When you are comparing the prices of two different pairs of shoes, you are using money as a unit of account to measure their respective values in monetary terms (e.g., dollars, euros, etc.).
Given the context of the question, when you are comparing prices, you are employing money as a benchmark to measure and compare the values of the shoes. Therefore, in this situation, money is being used as a:
unit of account.