Oliver was towards the very far side of the library

She sits down at a table near the corner.

Vivi checks her book back in before going to quietly look for a different one.

He was explaining quadratic equations to the fellow student

After a short-feeling half hour, the morning bell rings. It's a single chime; the singular one tells they have ten minutes before class starts, two chimes means they have three minutes, and a long gong-like sound tells class is starting.

She's all good with hopping off to class at the first bell. She didn't like risking being late. And so she gave up on looking for a book and spun on her heels, carefully making her way to the library exit.

Oliver wrapped up the lesson, sending the other student on their way

It becomes very quiet. Trix is still in the library near a corner.

Vi notices Trix as she walks to the exit, pausing. 'What if she becomes late for class? It is the first bell, yes of course. But what if her class is far? Oh, maybe i shouldn't worry. But ... ' She thought, having an inner battle before quietly going over to her.

Oliver takes his leave