The question should not be solved at excel

Your company owes a supplier company 430000 USD; the deadline for the payment is today. However, your company experiences short-term liquidity problems and you ask to postpone the payment for 27 days. The supplier agrees to postpone the payment on the condition that daily interest on arrears (fine for delay) is 0.05%; this is accrued based on the principle of simple interest. You can also borrow money from a bank - the bank is ready to provide a short-term uncollateralized loan at 15% per annum (let's assume that you can get the loan immediately). Interest on loan is accrued on the principle of continuous compound interest, the basis is ACT/365.

• Which alternative is less costly for your company? What's the annual rate of return the supplier company earns should you choose to postpone the payment (i.e. you agree to pay interest on arrears)?

What should annual interest rate on the loan be so that two alternatives are equivalent?