One of the three shops on campus that sell university logo clothing has found that if it sells a sweatshirt for $30 or more, the other two shops keep their prices constant and the store loses revenues. if, however, the shop reduces its price below $30, the other stores react by lowering their prices. what kind of market structure does this store face? if the store's marginal costs fluctuate up and down very slightly, how should the store adjust its prices?

Google started as one of many internet search engines, amazon started as an online book seller, and ebay began as a site where people could sell used personal items in auctions. these firms have grown to be so large and dominant that they are facing antitrust scrutiny from competition regulators in the us and elsewhere. did these online giants grow by fairly beating competition, or did they use unfair advantages? are there any clouds on the horizon for these firms -- could they face diseconomies of scale or diseconomies of scope as they continue to grow? if so, what factors may limit their continued growth?