Practice Problem $2$

Your parents start saving for your sister's college education. She will begin college at the age of $18$ and will need $$4,000$ per year at the end of each of the following four years she stays in college. Tuitions are paid after starting college. They will start to make a deposit one year from today in an account which pays $6\%$ compounded annually and they continue making an identical deposit until the year your sister starts college. If a deposit of $$1,987$ will allow them to reach their goal, how old is your sister?