A homeowner took out a 30-year, fixed-rate mortgage of $310,000. The mortgage was taken out 10 years ago at a rate of 7.50 percent. If the homeowner refinances, the charges will be $2,500. What is the highest interest rate at which it would be beneficial to refinance the mortgage? (Do not round intermediate calculations. Round your answer to 2 decimal places. Omit the "%" sign in your response.)

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