“…Now let us formulate the retailer problem. Similarly to the producer problem (2.5) (see [13,14]), let d R be the retailer's marginal costs and F R be the retailer's fixed costs. Let p * (i, r(i), N, P ) be the optimal pricing policies, then the demand is q(i, r(i), N, P ) while the profile of mark-up is r = (r(i)) i∈[0,N ] .…”