with steps please

Mapple is a smartphone producer who operates its own stores and directly sells its products to its customers. The variable cost of their smartphone is $200, which Mapple sells at 300% markup. Recently, Mapple decided to sell some of its smartphones through another retailer. Accordingly, they sell their smartphones to a wholesaler at 25% markup, who then sells the smartphone to the retailer at 50% markup. If the retailer intends to sell these smartphones at the same price as Mapple does in their Mapple stores, what is the contribution margin ($) of the retailer? O a $625 O b. $425 O c. $525 O d. $325