math

You purchase a computer for $755.00 plus 5% sales tax. You decide to finance it through the store's 0% interest program for six months. The terms state you must pay $50.00/month and that if you miss a payment, you will be assessed a late fee of $39.00 plus the interest accrued to that point at a 17.25% APR. If you miss a payment in the fifth month, how much interest will you be charged?