Please comment on the following sentence by providing a proof it true, or a counter-example if false: "If in a continuous double auction after a trade the range of moving equilibrium prices (i.e., the competitive equilibrium price range of the demand and supply schedules that remain after removing the values and costs of the units involved in the trade) does not coincide with the range of competitive equilibrium prices (i.e., the competitive equilibrium price range of the initial demand and supply schedules), then it must be the case that the level of efficiency in the trading period can never equal 100%."