Can some one please help with this? I know B. to be correct and am having difficulty with A. & C. Thank you!

Company X sells on a 1/20, net 90, basis. Company Y buys goods with an invoice of $4,500. a. How much can company Y deduct from the bill if it pays on day 20? (Do not round intermediate calculations.) Discount b. How many extra days of credit can company Y receive if it passes up the cash discount? Number of days c. What is the effective annual rate of interest if Y pays on the due date rather than day 20? (Use 365 days in a year. Do not round intermediate calculations. Enter your answer as a percent rounded to 2 decimal places.) Effective annual rate