Accounts payable are due 30 days after the invoice statement date.There is no opportunity for a discount by paying early.However, there is a 1.5% charge per month, if payment is late:If payment is after 30 days, the 1.5% charge is applied.If payment is after 60 days, the charge is 3%, etc.

An historical review of invoices shows that the dollar-weighted average of payment dates was 40 days after the invoice statement dates.In other words, on average, invoices were paid 40 days after the statement dates.No invoices were paid within 30 days, and none after 60 days.If the tax rate is 24%.

Estimate the effective annual after-tax interest rate for funds obtained this way (three significant digits).

Show some work for this problem.