Price Price p* (a) Quantity (b)Q* Quantity (a)For a horizontal demand curve,(%AQ/%P)is infinite. Because a tiny change in price leads to an enormous change in demand, the elasticity of demand is infinite. (b)For a vertical demand curve,(%AQ/%AP)is zero. Because the quantity demanded is the same no matter what the price is, the elasticity of demand is zero.Quantity Quantity (a) (b) P* D Q* D Price Price (a) For a horizontal demand curve, (%△Q/%△P) is infinite. Because a tiny change in price leads to an enormous change in demand, the elasticity of demand is infinite. (b) For a vertical demand curve, (%△Q/%△P) is zero. Because the quantity demanded is the same no matter what the price is, the elasticity of demand is zero