If you buy something and sell it later on the same day, how do you calculate 'investment'?
Not sure if your question is on topic, but the investment is only $9 because that is maximum amount of money the merchant ever needed to start up the business. He put in $9, started turning a profit, and never looked back.
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
If you buy something and sell it later on the same day, how do you calculate 'investment'?

### Response:
Not sure if your question is on topic, but the investment is only $9 because that is maximum amount of money the merchant ever needed to start up the business. He put in $9, started turning a profit, and never looked back.