fixed cost is group of answer choices the total expense incurred by a firm in producing and marketing a product, which equals the sum of overhead cost and variable cost. the change in expenses that results from producing and marketing one additional unit of a product. the average amount of money received for selling one unit of a product or simply the price of that unit. the sum of the expenses of the firm that are stable and do not change with the quantity of a product that is produced and sold. the sum of the expenses of the firm that vary directly with the quantity of a product that is produced and sold.