Ken makes $1200/month. He is applying for a mortgage to buy a house that requires at most 40% back-end PTI. The underwriter determines that taxes and insurance for the house would cost $89 monthly. The underwriter also determines that his other debt monthly payments (credit card, student and auto loan) are $79. What is the maximum qualified mortgage monthly payment that Isak can have acording only to the underwriter's back-end PTI rule?