If you are age 25, single, wage income of $50,000, 401(k) at work, and invest $1,000 into a Roth IRA, what is your spending power at age 70? Assume your tax rate now is 15%, your tax rate in retirement is 20%, and the pretax annual return on the investment is 5%.

a.) $7,188

b.) $7,637

c.) $8,985