Joan Begins the Month with $100 in Her Checking Account

Joan begins the month with $100 in her checking account. When she receives a pay check for $1,200 on the 5th of the month, she uses that pay check to put $1,000 in her checking account, takes $80 in cash, and deposit $120 in her savings account. During the month, she spends $550 on rent and utilities, $30 on household items, $10 on a T-shirt, and $350 on food, leaving a balance of $240 in her checking account. Based on the given information, which statement accurately describes the function of Joan's money?

A) Savings is a store of value measured in units of account.
B) Her expenditures use funds as a medium of exchange but with no role for money as a unit of account.
C) Buying goods and services uses money as a store of value and unit of account.
D) Depositing money in savings is using it as a medium of exchange.