The dollar price for a barrel of oil sold at a certain oil renery tends to follow the demand equation below, where x is the number of barrels of oil on hand (in millions). a) How much should be charged for a barrel of oil if there are 7 million barrels on hand? b) What quantity x will maximize revenue? c) What price should be charged in order to maximize revenue? 1 p= -;x+155 a) What should be charged for the units in stock? $ (Round to the nearest cent as needed.)