capkid007 发表于 2014-10-1 01:34 
上次那个帖子是不是被删掉了。。本来有道题 现在重新po在这里吧
return to the final example of sectio ...
Problem 6
Profits if it serves only North America
Qn = 100 - Pn -------> Pn = 100 - Qn
MRn = 100 - 2Qn
Now, equate marginal revenue in North America with marginal cost.
100 - 2Qn = 20 --------->Qn = 40
Pn = 100 - (40) = 60
Hence, Pie N = (Pn - 20) Qn = (60-20)(40) = 1600
Profits if it serves both Sub-Saharan Africa and North America
Aggregate Demand is Qa = (1+a)100 - 2P
In that case, marginal revenue is MRa = (1+a)50 - Qa
Equate marginal cost with marginal revenue
(1+a)50 - Qa = 20
Qa = (1+a)50 - 20
Hence, Pa = (1+a)25 +10
Therefore, PieA = (Pa - 20)Qa = 2[(1+a)25 -10]^2
Now, equate , PieA = PieN or equivalently
2[(1+a)25 -10]^2 = 1600 -----------> a= [(40/squrt2 +10)/25 ] -1 = 0.531