Interest on Credit Cards. Eileen, who is currently paying $2,575 per year in finance charges to her credit card company, wants a car that costs $14,000. How long would it have taken Eileen to save for the outright purchase of the car if she did not have any credit card debt and used the interest payments to save for the purchase of the car? Eileen can invest funds in an account paying 6% interest. To save for the outright purchase of the car, it would take Eileen years.