Lydia is a senior in high school. She works 20 hours a week at a popular clothing store. She is trying to save as much
money as possible for her college tuition. However, she has to buy a dress for prom, pay her car insurance, and get a
birthday gift for her sister. This week she received a $400 paycheck. She wants to deposit the entire check in her savings
account for her college tuition, but she stops herself. She decides instead to put $100 in the bank, spend $200 for her
prom dress, pay $80 for her car insurance, and buy her little sister a $20 birthday gift. While shopping, she sees a doll
worth $21, which she thinks her sister will absolutely love. As a result, she decided to buy the more expensive doll and
spend less on her dress.
What is Lydia's scarce resource?