Suppose that the market for a children's book is given by the following demand and supply functions: Demand: QD= 70 - 2P Supply: QS= -10 + 2P Where: QD and QS are quantity demand and quantity supplied respectively, and P is the price. Now suppose that, in an attempt to support the book publisher, a minimum price per book (price floor) is set at $25. The efficiency loss (deadweight loss) resulting from the price floor is equal to $ ____