4. (a) If a system has a planning horizon of 100 years, I = 6%, Amplitude 500 at t = 8, Amplitude 100 at t26, Amplitude = 600 at t = 50. Starting at t= 51 the amplitude decreases each year by 5 until t = 100 (A = 595 at 51 A = 590 at t = 52 and so on until 100). All other amplitudes are zero (for example t = 14 A-0 t = 15 A = 0). What is the present worth? (b) A system has a planning horizon of 90 years and Amplitude = 100 at t = 8 Amplitude 200 att 22, Amplitude is uniform at A = 100 from t = 40 tot = 70. Amplitude = 0 everywhere else. For interest rate, 1 - 3% for t=0 to t = 30,16% fort = 30 to t = 60, 1 = 12% fort 60 tot 90. What is the Future worth of the system at t= 90