You have a balance of $12,000 for your tuition on your American Express credit card. Assume that you make no more charges on the card. Also assume that American Express charges 21% APR and that each month you make only the minimum payment of 6% of the balance. What percentage of the previous balance is paid off each month? Round the percentage to two decimal places. (Hint: Construct a formula for the balance after t minimum payments and simplify the decay factor in order to answer this question.)