precisely 15 years ago( you have just made the 180th monthly payment) you took out a traditional, fixed rate30-year mortgage for$500,000 at 6.8% APR. you are considering whether to refinance this loan and replace it with a fixed rate 15-year mortgage(assume an identical timing of the remaining payment). The closing costs are $3000, which you intend to borrow. Disregarding the psychic cost of the process, please find the break even interest rate(I.e. the rate at which you would be indifferent between refinancing vs. keeping the existing mortgage)