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.

did lydia make an all-or-nothing or a marginal decision while spending her money? justify your response.