A document that refers to a customer billing for merchandise bought on credit is called a(n):

Invoice

Explanation:

A sales transaction can be defined as a business transaction between two or more individuals or organizations, which generally involves the buyer purchasing either a tangible or intangible goods and services from the seller (service provider) through the use of money, credit cards or vouchers.

An invoice can be defined as an accounting document which is used for recording the essential details of the payment of goods and services made by a customer. It is the first step in the sales transaction, as it is expected that the seller or service provider makes it available and issues it for all sales transactions. Also, it is an essential accounting document which serves as an evidence of payment and delivery of goods and services to the customer.

In conclusion, a document that refers to a customer billing for merchandise such as finished goods like television, smartphone, shirt, trouser, cup, radio, furniture, etc., bought on credit is called an invoice.

in terms of experimental research, mcdonald’s charging different prices in the two cities relates to