2 Suppose an industry is characterized by a firm with cost f
Solution
Ci = 2yi2 +100
D = 45 - (1/2)P
P = 90 - 2D
The firm considers the industry to be competitive then it would maximize it\'s profit by setting price equal to MC
Diff. The Cost function with respect to Y we get
MC = 4y
P = MC
90 - 2D = 4 y ( D = y= quantity)
90 - 2y = 4y
4y + 2y = 90
6y = 90
y* = 15 units
P* = 90 - 2×15 = $60 / unit
b. Short run profit = TR - TC = 60×15 - (2×152 + 100)
= 900 - ( 2×225 + 100) = 900 - 550
Short run profit = $ 350
c. Under monopoly price is set where MR = MC
TR = Py =(90 - 2y)y = 90y - 2y2
MR = 90 - 4y
Equating MR to MC we get
4y = 90 - 4y
8y = 90
ym = 11.25 units
Pm = 90 - 2ym = 90 - 2×11.25 = 90 - 22.5
Pm = $ 67.5 / unit
d. Profit (Monopoly) = TR - TC
?m = 67.5×11.25 -(2×11.252 + 100)
= 759.375 - 353.125
= $ 406.25
Profit (?m ) of monopoly is greater than profit under competitive market structure.

