What system developed in medieval Europe in which knights or vassals served and protected kings or nobles in exchange for land

Cooperation among oligopolies runs counter to the public interest because it leads to underproduction and high prices. in an effort to bring resource allocation closer to the social optimum, public officials attempt to force oligopolies to compete instead of cooperating. consider the following scenario: suppose that the presidents of two auto manufacturing companies exchange text messages in which they discuss jointly raising prices on their new lines of hybrid suvs. this illegal communication would violate which of the following laws? the sherman antitrust act of 1890 the robinson–patman act of 1936 the celler–kefauver act of 1950 the clayton act of 1914