Revisit the first example covered in the chapter on "Optimal Product Mix." Consider all constraints but $-$ in addition $-$ assume that, whenever you sell more than $320$ units $($pounds$)$ of any product, you must give a discount of $$1\mathrm{.}00$ per pound on each pound above $320$ sold.

What is the optimal product mix, total labor and material used and maximum profit subject to all these constraints?