Suppose you have a 5/1 Interest only ARM with a 5-year teaser rate of 3%, a 30 year loan of $400,000, , and a 2% per year cap. The loan is interest only for the first 5 years, and becomes fully amortizing after that. The LIBOR is 2% and used as index. The margin is 3%.

These terms were common prior to the housing crisis. After 5 years, the LIBOR rises to 4%. Calculate the growth rate (%) of mortgage payment in at the beginning of year 6.