Suppose that in an open economy, the consumption function C = 300+ 0.8YD, the investment function I = 200-1500R, the net export function NX = 100+ 0.04Y-500R, the money demand function L = 0.5Y-200R, the government expenditure G = 200, the tax function T = 0.2Y, and the nominal money supply M = 550. The price level P is equal to 1. O:

(1) IS curve equation;

(2) LM curve equation

(3) Income and interest rate when product market and money market are simultaneously in equilibrium.