A homeowner took out a $20-$year fixed$-$rate mortgage of $$175,000.$ The mortgage was taken out $7$ years ago at a rate of $6\mathrm{.}75$ percent. If the homeowner refinances, the charges will be $$2,850.$ What is the highest interest rate at which it would be beneficial to refinance the mortgage?

Note: Do not round intermediate calculations. Enter your answer as a percent rounded to $2$ decimal places.

What is the APR$\%$