For firms in perfectly competitive markets, the amount by which the total revenue rises when one more unit is sold is called the , and this is equal to the

You are in the market for a new refrigerator for your company’s lounge, and you have narrowed the search down to two models. the energy efficient model sells for $700 and will save you $45 at the end of each of the next five years in electricity costs. the standard model has features similar to the energy efficient model but provides no future saving in electricity costs. it is priced at only $500. assuming your opportunity cost of funds is 6 percent, which refrigerator should you purchase