Answer: (1) Equilibrium price = 60 and Equilibrium quantity = 120, when I = $1500.
(2) Equilibrium price = 54 and Equilibrium quantity = 108, when I = $1200.
Explanation:
(1) When Average income (I) = $1500
At equilibrium, QD = QS
150 - 3p + 0.1I = 2p
150 - 3p + 0.1 × 1500 = 2p
5p = 300
p =
p = 60
q = 2p ⇒ 2 × 60 = 120
Hence, p and q are equilibrium price and equilibrium quantity, respectively.
(2) If 20% income tax is introduced then Average income (I) = $1500 - 20% of $1500 ⇒ $1500 - $300 = $1200
At equilibrium, QD = QS
150 - 3p + 0.1I = 2p
150 - 3p + 0.1 × 1200 = 2p
5p = 270
p =
p = 54
q = 2p ⇒ 2 × 54 = 108
Hence, p and q are equilibrium price and equilibrium quantity, respectively.