A firm offers terms of 2/15, net 60.

a. What effective annual interest rate does the firm earn when a customer does not take the discount? (Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.)

b. What effective annual interest rate does the firm earn if the discount is changed to 3 percent? (Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.)

c. What effective annual interest rate does the firm earn if the credit period is increased to 80 days? (Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.)

d. What effective annual interest rate does the firm earn if the discount period is increased to 20 days? (Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.)