Brad buys a house in Fermentation Station, NJ for $600,000. He pays 18.5% as a down payment today, and he will finance the remainder of the loan. He will make 60 equal monthly payments of $13,000, beginning one year from today, plus a balloon payment one month after the final $13,000 payment, which will completely pay off the remainder of the loan. If the stated annual interest rate is 18%, compounded monthly, find the balloon payment that Brad will make at that time.

The answer is 108955, but I don't know how to calculate. Could you show your works please? Thank you!