One question

[avkuvalekar]

Hi Guys,

One more macro question for you guys.
I solved this one but my answer isn't matching with the one given in the solutions. There is no detailed explanation as to how they got it.
As said on numerous occasions previously, I have no economics undergrad in my knowledge which forces me to post this here.
Any help will be greatly appreciated.

Consider an IS-LM model for a closed economy with government where investment (I ) is a function of rate of interest (r) only. An increase in government expenditure is found to crowd out 50 units of private investment. The government wants to prevent this by a minimum change in the supply of real money balance. It is given that dI/dr = -50 , slope of the LMcurve,dr/dy = 1/250 , slope of the IS curve,dr/dy = -1/125 , and all relations are linear. Compute the change in y from the initial to the final equilibrium when all adjustments have been made.

[avkuvalekar]

I solved it this way -
50 units of private inestment was crowded out. dI/dr = -50. So, The interest rate increased by 1 %.
Now, I need to find the base in the small triangle that is formed with the three points as
initial equillibrim, final equilibrium (the right most point, same interest rate with increased G causing Y to increase, the intermediate point where an increment in G caused r also to increase)
So, the base of this triangle is the net change in Y following all the adjustments.
This base is 250 + 125 = 375.
The answer given is 50. It could be that the way I am applying the crowding out information is wrong.
Can someone help me out please?