Illustration $5($for students$)$

Suppose you are expecting to earn $45,000$ a year for the next $40$ years and anticipating $20$ years of retirement

i$.$ You are expecting zero real interest $($interest net of inflation$).$ How much should be saved for retirement on $\frac{2}{3^{rd}}$ income; and

ii$.$ You are expecting real rate of interest on $5\%$ p$.$a$.$