In 2008, cruise ship lines announced they were increasing prices from $7 to $9 per person per day because of increased fuel costs. according to one analyst, fuel costs for carnival corporation's 84-ship fleet jumped $900 million to $2 billion in 2008 and its cost per passenger per day has jumped from $10 to $33. assuming that these firms are oligopolistic and the outcome is a nash-cournot equilibrium , why did prices rise less than in proportion to per-passenger-per-day cost? at the cournot equilibrium, prices rose less than in proportion to per-passenger-per-day costs because a. the number of firms must have decreased. b. marginal costs do not affect oligopoly prices. c. consumers are infinitely price sensitive. d. consumer demand is not perfectly inelastic. e. only fixed costs affect oligopoly prices.