The demand for a product is Qd = 100 - 4P +3Px and supply is Qs = 10 +2P, where Q is the quantity of the product in thousands of units, P is the price of the product, and Px is the price of another good. When Px = 40, the equilibrium price of the product is 35 and the equilibrium quantity is 80 thousand units
At the equilibrium price and quantity, the price elasticity of demand for the product is ___?