Taking mine in September would love to join!

Interested!

I would love to join!

It's my first time explaining. Sorry if I make a mistake. This is how I thought of it.

First, let's look at each sentence and translate them into lawgic.

Unless a bookstore generates high sales volume, it cannot get bulk discounts from publishers.

We have both a group 3 or 4, but we have to choose one of them. I used unless since it made more sense grammatically to me.

I italicized the assigned symbols and now we need to apply the transition rules (negate, sufficient).

/volume → /discount

To generate high sales volume, a bookstore must carry popular books.

Here we have group 2 (necessary).

volume → popular

Okay, so we have these two translations.

In order to be able to chain it we need to get the contrapositive of the first translation. Which is:

discount → volume

Now we chain them together.

discount → volume → popular

discount → popular

In other words, "getting bulk discounts from publishers requires carrying popular books."

Hope that helps a little :D