If the price of an airline ticket from JFK to LAS were to increase by 20%, from $250 to $300 roundtrip, while all other demand factors remain at their initial values, the quantity of rooms demanded at the Peacockfalls from 200 rooms per night to 100 rooms per night. Because the cross-price elasticity of demand is negative, hotel rooms at the Peacock and airline trips between JFK and LAS are substitutes.