Suppose that the demand and supply functions for good x are given as follows: Of = 600-2P - I+ P, and OR = Px - 21 +s-2f where Px denotes the price of good x, P, denotes the price of a related product y, I denotes income, t denotes tax firms face, s denotes subsidy and f denotes factor prices. What is the nature of the relationship between products x and y? O and They are substitutes since since =1>0 aPy O aQa They are substitutes since since =-1