This describes the problem with the argument failing to establish the total earnings from each sale. Even if the profit margin is smaller, an expensive item can still generate a much higher profit than a cheap one.

The number of sales last year is irrelevant because the manager’s argument is based on the prediction that the store would sell the same number of models if it sold the low-end ones exclusively.

This is irrelevant. It only matters what customers actually purchase, not what they expect to purchase.

This is descriptively inaccurate. The manager seems to believe that maximizing profits is a sufficient reason to sell certain products, but doesn’t claim that it should be the store’s only objective.

The manager establishes in a premise that the store would probably sell as many total models if it sold low-end computers exclusively compared to selling both low-end and high-end. This acknowledges the possibility that future sales of low-end models might not be the same as past sales of those models. In fact, the argument contemplates selling more low-end models overall by switching to low-end models exclusively.