I understand how the present value is set up, but my first instinct was to use an annuity when I saw this. How would I use an annuity to solve this problem?

15. Jason is planning for retirement and wants to have enough cash to withdraw $20,000 per year beginning 20 years from today (time 20) and continuing each year for 30 years after this (until time 50). How would you calculate the present value of the amount Jason needs? Set up your calculation in detail but do not solve (6 points). PV = 20000/(1+r)20 + 20000/(1+r)21 + ... + 20000/(1+r)50 Note there are 31 payments of 20,000 here, so this will be a 31 period annuity if you are setting it up that way. Also the 31 period annuity would have to be discounted by 19 periods. To check your answer, if r=5%, the PV is $123,412.09 15. Jason is planning for retirement and wants to have enough cash to withdraw $20,000 per year beginning 20 years from today (time 20) and continuing each year for 30 years after this (until time 50). How would you calculate the present value of the amount Jason needs? Set up your calculation in detail but do not solve (6 points). PV = 20000/(1+r)20 + 20000/(1+r)21 + ... + 20000/(1+r)50 Note there are 31 payments of 20,000 here, so this will be a 31 period annuity if you are setting it up that way. Also the 31 period annuity would have to be discounted by 19 periods. To check your answer, if r=5%, the PV is $123,412.09