Which of the following is NOT true about the in-app billing?

In-app billing is a monetization technique that allows you to sell products through your application during its run-time.

For this feature to be implemented in the application, it must be a paid application.

In-app billing technique can be used for both paid and free applications.

The products that can be sold through this technique might include application features, game items, hints, articles or any other product that can be processed in your application.