How to store pictures in android app locally?

Question

Android

The application must contain pictures with formulas. The application is local, there is no server. And so a question in how to store pictures of these formulas. Many advise to store in external storage, but I can’t understand, because I need to put these pictures into the application somehow. Is it ok to load in assets?
UPD: Another separate question. I know about Firebase, you can also store data there. But I can’t understand, there is a free plan and there is a request limit, and so, is this limit enough for a full-fledged application if at least 100 - 200 people use it.

Answer 1

Assets is fine. Quite.

Answer 2

Create page template ?