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?