Following the notations: 12 represents the cross elasticity of the quantity demanded for good 1 when the price of good 2 changes, "" for bicycles, "" for skateboards, and "" for unicycles. The cross-price elasticity of the quantity demanded for unicycles when the price of bicycles changes is = 2, and the cross-price elasticity of the quantity demanded for skateboards when the price of bicycles changes is = 1.5. According to the price change between part (a) and part (b), calculate the percentage change in quantity demanded for unicycles and skateboards. Use your results to explain how unicycles and skateboards are related to bicycles. Hint: Use the midpoint formula.