好象你说的对,,,因为 弹性确定,例如q=a-bp,-bp/q=-3,bq=3p,mc=a-2bp=a-3q,由mc多6,q多2单位所以p增加多少 应该与b有关,对吧?

Assume that, P=a-bQ,MR=a-2bQ.

At the point E0, on which Ed=-dQ/dP*P0/Q0=1/b*(a-bQ0)/Q0=3, therefor,a-bQ0=3bQ0,a=4bQ0,

P=4bQ0-aQ,P0=4bQ0-bQ0=3bQ0

More over, MC(Q0)=MR(Q0),MR(Q1)=MC(Q1)=MC(Q0)+6=2bQ0+6.

P1=4bQ0-bQ1,MR(Q1)=4bQ0-2bQ1=2bQ0+6,2b(Q0-Q1)=6,deltaQ=Q1-Q0=-6/2b

deltaP=P1-P0=(4bQ0-bQ1)-(4bQ0-bQ0)=-bdeltaQ=b(Q0-Q1)=6/2=3.

To sum up, deltaP=+3

[此贴子已经被作者于2006-3-29 23:57:29编辑过]

More over, MC(Q0)=MR(Q0),MR(Q1)=MC(Q1)=MC(Q0)+6=2bQ0+6.

Thank you for your reply. But apparently you have made a mistake in deriving the above equation. Rearrange your equation, we get : MC(Q1)-MC(Q0)=6 , which could only be true under the precondition of constant MC. As a matter of fact, the MC curve itself has been changed after the tax, hence the only equation we can derive should be:

MC'(Q1)-MC(Q1)=6 or MC'(Q0)-MC(Q0)=6 Where MC' is the new mc function.

由P=a-bQ,MR=a-2bQ得ＭＲ＝２Ｐ－a。所以Ｐ的变化量为ＭＲ的一半。ＭＲ的变化量等于ＭＣ的变化量，但他们都小于６（只有征税前后产量不变时ＭＣ的变化量才是６，但征税后产量下降，ＭＣ的增加小于６）。所以准确答案应该是小于３。

you bet.i was wrong.

i totally was wrong, i should not have been married. if i was not married...