Find the amount that you will have in your retirement account: (1) in 10 years at 5% if you invest $1,000 per year; (2) if you leave the $100,000 you have there now and do not invest anything additional for the next 10 years if you earn 6% per annum; (3) if you add $1,000 per year for the next 7 years to the $100,000 you have already and you earn 4% per annum on the whole account.

How much would you need to invest today in order to have (1) $15,000 in 5 years at 10%; (2) $50,000 each year for 50 years at 5%; (3) $7,000 each year for 10 years at 8%; (4) $20,000 at the end of 12 years if you earn 3% per year?