8. Given the following model to describe our economy: Y=C+I + 250 C = 50 +0.7 (Y T) I= 150 - 100 750 = Y - 501 Where Y CI and r stand for the endogenous variables national income, consumption expenditure, investment and interest rate respectively. T is government tax, an exogenous variable. a. If T =$ 200 million. Find the equilibrium national income using repeated substitution method. b. Investigate the effect of a $50 million decrease in government taxes on income