Final answer:
Money is being used as a unit of account when estimating monthly income and expenses.
Step-by-step explanation:
When estimating your monthly income and expenses, money is being used as a unit of account. This means that money provides a common measure for valuing goods and services. It allows you to assign a specific value to different items, making it easier to calculate and compare income and expenses.
For example, if you have a monthly income of $1000 and your expenses include rent ($500), groceries ($200), and utilities ($100), you can use money as a unit of account to understand how much of your income is allocated to each expense category. In summary, money serves as a unit of account when estimating monthly income and expenses, helping you track and analyze your financial situation.