Final answer:
Accepting a special order below current selling price is advisable when incremental revenues outdo the incremental costs and no extra fixed costs are involved, unless it affects the current market negatively.
Step-by-step explanation:
When there is excess capacity, it may make sense to accept a one-time special order for less than the current selling price if incremental revenues exceed incremental costs, and if the order does not affect existing operations or sales in the current market. Accepting the special order could be beneficial even if the special order pricing is lower than standard prices, provided that no additional fixed costs need to be incurred. However, if the company placing the order competes in the same market segment as the firm's current customers, accepting the order at a reduced price might not make sense since it could undermine the current pricing strategy and lead to potential conflicts with existing customers.