Your business provides CDs on learning English that compliment the teaching that is provided by your employees based in Mexico. Assume that you decide to capitalize on these CDs by selling them to a large retail store based in Mexico. The CDs are not as effective without the teaching, but can be useful to individuals who want to learn the basics of the English language. You do not want to take the risk of sending a case of CDs to the retail store unless you can be sure of receiving payment. Explain how you can ensure payment for the CDs.