It is July 1, and Eduardo wants to purchase an engagement ring for his soon-to-be fiancée. He visits several jewelry stores and finds the perfect ring. The cost of the ring is $1,800. Eduardo doesn't want to put the purchase on a credit card, so he decided to put the ring on layaway. Since he needs the ring in 6 months so that he can propose on New Year’s Eve, he agrees to pay the store $300 per month. Since Eduardo knows exactly how much money he needs to pay each month, this is a(n) __________ goal