申論題

6. (20%) Suppose that the demand curve for a particular commodity is Q^D = α-βP, where Q^D is the quantity demanded, P is the price, and α,βare constants, both larger than zero. The supply curve for the commodity is Q^s =γ+δP, where Q^s is the quantity supplied, P is the price, and γ,δare constants, δ＞ 0. Prove aleebraically that the post- tax equilibrium (consisted of a consumer price, a producer price, and the quantity associated with these prices) is the same regardless of whether the tax is imposed on consumers or producers.