The following equations describe an economy. (Think of C, I, G, etc., as being measured in billions and i as a percentage; a 5 percent interest rate implies i= 5.)C =0.8(1- t)Y(P1)C depends on MPC and disposable incomet = 0.25(P2)t is the marginal tax rateI= 900 -50 i(P3)i is the interest rateG= 800(P4)L = 0.25Y- 62.5i(P5)M/P = 500(P6)a . What is the equation that describes the IS curve?b . What is the general definition of the IS curve?c . What is the equation that describes the LM curve?d . What is the general definition of the LM curve?e . What are the equilibrium levels of income and the interest rate?