A couple retires today with their savings of 350,000. They invest all the money in a bank account which pays 2.5% interest per year, compounded annually. They plan to withdraw 15,000 at the beginning of each year with the first withdrawal occurring immediately. They also plan to have a balance of 70,000 in the account for their children when they stop withdrawing the money from the account. For how many years could this couple make the 15,000 withdrawals and still leave 70,000 for their children