On a $5000 purchase (including sales taxes) under a no-interest and nothing-to-pay-for-one-year promotion, how much interest will

Question:

On a $5000 purchase (including sales taxes) under a “no-interest and nothing-to-pay-for-one-year” promotion, how much interest will you be charged for the grace period if you are one day late on your payment of the principal? Use an interest rate of 28.8% compounded monthly.