In an SM-LM model economy the consumption function : C(Y-T)=100+0.5(Y-T). The investment function is I(r)=1000-20r, government purchase (G) is 400. net tax (T) is 300. The equation isY = 1500+100r. where r is real interest rate in percentage points.1) Derive the IS curve of the economy in a form similar to that LM curve above.2) Calculate equilibrium interest rate and income3) calculate what the change in GDP would be, if the government reduced the net tax but it would not change investment function.

----i guess we should use Y=C+I+G formula. please show steps thanks

dont answer by pen paper