Question

Erik has a five-dollar bill. He uses it to pay for a soda and a hamburger. What form of financial exchange is this?

Answer 1

If Erik is using a $5 in cash and buys soda and a burger, he's using a cash exchange for his purchase.

Answer 2

This purchase of product for a fixed amount.

I don't know your curriculum so i don't know if you are looking for  particular vocabulary or what.

I hope this helps.