In order to calculate marginal cost, producers must compare the difference in the cost of producing one unit to the cost of a. purchasing a unit. b. distributing that unit. c. producing the next unit. d. producing a different unit.

Correct  C. producing the next unit

According to Investopedia, marginal cost is defined as "the change in total cost that comes from making or producing one additional item."  Manufacturers will analyze the cost of producing one item over against producing additional quantities of the same item to determine at what point they achieve a sufficient reduction in the price of production to make production profitable.  So let's say I am able to produce a whatchamajig at a cost of $100, most of which was for setting up my whatchamajig-making machine.  If I make a second whatchamajig, because I've already got the whatchamajig-making machinery in place, the cost drops to $99 for each whatchamajig.  As I continue my analysis, I find that after costs of materials and my labor time, I can make 100 or more whatchamajigs for under $10 each, that becomes a point at which I think I can market my whatchamajigs at a price the market will pay and make my production profitable.

the correct answer is C. i just took the test

most people were factory or company owners.

porter is writing economic history because he is focusing on the cost of developing vaccines.