Press Now Corporation,a Disk Manufacturer,sells Its Product in Certain Quantities

Press Now Corporation,a disk manufacturer,sells its product in certain quantities to Quik 2U,a retailer,for $275 but charges Rite Here,a competitive retailer,$350.Under the Clayton Act,this is legal

A) under any circumstances.
B) unless its effect is to cause a competitor a loss of any business.
C) unless its effect is to substantially lessen competition.
D) unless there is no effect on a competitor.