how to solve this?

A firm offers terms of 2.6/7, net 30. a. What effective annual interest rate does the firm earn when a customer does not take the discount? (Use 365 days a year. Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.) Effective annual interest rate 51.92 % b. What effective annual interest rate does the firm earn if the terms are changed to 3.6/7, net 30, and the customer does not take the discount? (Use 365 days a year. Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.) Effective annual interest rate 78.81 % c. What effective annual interest rate does the firm earn if the terms are changed to 2.6/7, net 45, and the customer does not take the discount? (Use 365 days a year. Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.) Effective annual interest rate 28.80 % d. What effective annual interest rate does the firm earn if the terms are changed to 2.6/12, net 30, and the customer does not take the discount? (Use 365 days a year. Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.) Effective annual interest rate 70.63%