Where Several Products Are Produced and There Is a Scarce

Where several products are produced and there is a scarce factor, what is the rule for deciding on the optimum product mix?

A) Produce only the product with the highest contribution margin.
B) Produce only the product with the highest contribution margin per unit of scarce factor.
C) Produce as much as can be sold of the product with the highest contribution margin per unit of scarce factor, and use any remaining resource to produce the product with the next highest contribution margin per unit of scarce factor etc.
D) Produce equal quantities of all products.