3) A consumer's demand function for good x is Qx = 120 - 2Px - Py + Pz/2+ I/1000 with Qx representing the quantity demand for good x, Px the price for good x, Py the price for good y, Pz the price for good z, and I the consumer's income.

a) Determine the quantity demanded for good x if Px = Py = Pz = 20 and I = 2000.

b) Determine the inverse demand function for good x if Py = Pz = 20 and I = 4000.

c) Determine whether good y is a complement or substitute to good x.

d) Determine whether good z is a complement or substitute to good x.

e) Determine whether good x is a normal or inferior good.