The supplier of the soft drink for the beverage company is offering the following quantity discounts on the price of the can:

Quantity Purchased Per$-$Unit Price

$1$ to $699$ $$3\mathrm{.}2$

$700$ to $999$ $$3\mathrm{.}1$

$1000$ or more $$2\mathrm{.}9$

$1.$ Determine the quantity that the company should order under each of the discount models:

$($A$)$ Incremental Quantity Discount:

Discounts are applied incrementally, with each tier's pricing affecting only the units within that tier.

$($B$)$ All Units Discount:

Once a purchase exceeds the threshold of a discount tier, the discounted price applies to all units ordered.

Your task is to find the optimal order quantity for each discount model, considering how they impact the total purchasing and holding costs. Discuss which quantity discount model the beverage company should select.