Suppose you are running a hotdog stand. Each hotdog sells for $2, and costs you $0.75 for the meat and bun. Working alone, you can cook and sell 15 hotdogs an hour. If you purchased a new hotdog oven for $675, you could produce 40 hot dogs an hour.

Assume that you have $125 in cash, so you would need to borrow $450 to purchase the oven. What is the maximum interest rate you would accept to make the investment? That is, if the interest rate were higher you would choose to not make the investment. Assume the oven does not depreciate. Answer in percentage form.