A large retailer obtains merchandise under the credit terms of 3/20, net 40, but routinely takes 65 days to pay its bills. (Because the retailer is an important customer, suppliers allow the firm to stretch its credit terms.) What is the retailer's effective cost of trade credit? Assume a 365-day year. Do not round intermediate calculations. Round your answer to two decimal places.

Please also explain how you calculate the discount percent.