1. Determine the principal needed to accommodate the payouts. The formula is
i is the quarterly interest rate. Which is the rate divided by 4. .08/4 = .02.
P is the payout amount. $60,000
n is the number of payout periods. 16 - quarterly payments (4 per year) for 4 years.
A is the amount needed at the start of the annuity pay out period.
2. What is the amount he has to save now, so that it accumulates to that $830,955.81? PV = FV/(1+r)^n where r is the quarterly interest rate (.02), n is the number of quarters (20 years times 4 quarters per year = 80 quarters), and FV is the future value needed to support the annuity. That FV is 830,955.81.
PV = 830955.81/(1.02)^80 = $170,437.12