Assume the demand function for good x can be written as Qd = 80 - 3Px + 2PY + IOI, where Px is the price of x, py is the price of good y, and I = consumer income. According to this equation; 1. Because the coefficient on the px is negative, x is an inferior good. 2. x and y are substitutes 3. Because the coefficient on income is positive, x is a giffen good 4. x and y are complements