Let's see if we can formulate any real laws about the economics of taxation. Which of the following must be TRUE, as long as supply and demand curves have their normal shape (demand curves are downward sloping while supply curves are upward sloping)? If there is a tax: the equilibrium quantity must fall, and the price that sellers receive must rise.the equilibrium quantity must fall, and the price that buyers pay must rise.the equilibrium quantity must rise, and the price that sellers pay must rise the equilibrium quantity must rise, and the price that buyers receive must rise.