answers to one decimal place. a. if paid on time Approximate interest rate: % Compound interest rate: % b. if paid on the 45th day Approximate interest rate: % Compound interest rate: % c. if paid on the 55th day Approximate interest rate: % Compound interest rate: % Why does the cost change? The rate of interest as the firm rides the credit because it has the use of the funds for a time period and the interest cost