Gibbs Corporation Makes Indoor Gas Fireplaces

Gibbs Corporation makes indoor gas fireplaces.A standard fireplace includes unit-level materials,labor,and overhead costs.In addition,the company incurs product-level engineering and advertising costs.The sales staff is paid a 5% commission on each fireplace sold.A sales representative has been in contact with a building developer who wants to buy 20 fireplaces only if he can buy them at amount lower than Gibbs's selling price.Which of the following costs would be relevant to this special order decision?

A) The sales commissions
B) The product-level engineering and advertising costs
C) The unit-level materials, labor, and overhead
D) All of these answers are correct.