In: Economics
Suppose a monopolist is can price discriminate between two groups of consumers. Group 1 has demand function given by P1 = 100-2Q1 and group 2 has demand function given by P2 = 200-4Q2. Suppose this monopolist has constant marginal cost of $20 and zero fixed cost.
Calculate consumer surplus, producer surplus, and total welfare in this market.
The monopolist is charging different price from different markets. The monopolist will maximize profit at MR = MC
Equate it to MC
P1 = 100 - 2Q1 = $ 60 per unit
CS1 = (1/2)×(100-60)×20 = $ 400
PS1 = (100-20)×85 = $ 6800
Total surplus =$ 7200
Now calculate for market 2
Equate it to mc
P2 = 200 - 4×22.5 = 110 per unit
CS2 =0.5×(200 -110)×22.5 = $ 1,012.50
PS2 = (110-20)×22.5 = $ 2025
TS = $ 3,037.50
Now calculate the demand when P1 =P2 = P
P = 100 - 2Q1
Or, Q1 = 50 - 0.5P
P = 200 - 4Q2
Or, Q2 = 50 - 0.25P
Add these two equations we get
Q = 100 - 0.75P
P = (100 - Q)/0.75
Now equate it to MC
(100-Q)/0.75 = 20
100 - Q = 15
Qp = 85 units
P = $ 20
Total welfare under perfect competition = (1/2)×(133.33 - 20)×85 = $ 4,816.67