(1) Money demand function = money investment function + money transaction function = 0.25y+(10000/r-2)-1000=90010000/r-2?

（ 2) Not (3) 7% (4) When r=6, the income is 38,000, and when r=12, the income is 44,000.

For example:

Money demand is the sum of transaction demand and speculative demand. In total, that is, the money demand function is: L=0.4Y+3000-200r

Putting in r=5, Y=2500, we get zhiL=3000

Putting in r=10, Y= 2000, we get L=1800

Substituting L=4000, Y=3000, we get r=1, that is, the interest rate is 1%.

Extended information:

According to the national income accounting identity, in the two-sector economy, Y=C+I, that is, Y=40.8Y+120-5r, which can be summarized as, Y =800-25r is the IS equation; according to the equality of money supply and demand: 0.2Y-5r=100, Y=5025r

is the LM equation.

Let the IS and LM curves intersect, that is, 800-25r=5025r, the equilibrium interest rate is r=6, the equilibrium income is 650, substitute it into investment I, and the investment is 90.

Now IS remains unchanged, and the LM curve becomes 0.2Y-5r=150, that is, Y=7525r.

Recombine to find the equilibrium r=1, Y=775, I=115.

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