please help solve exercise 8,9

using Theory of interests formula (explain please)

8.-/1 points You will retire in 30 years. At the beginning of each month until you retire, you will invest X earning interest at 8% convertible monthly. Starting at year 30, you will withdraw $3,300 at the beginning of each month for the next 15 years. Also, starting at year 30, your fund will only earn interest at 6% convertible monthly. Find X such that your account will be empty after the last withdrawal. Answer = $ (round your answer to 2 decimal places.) 9.-/1 points Find the present value of payments of $200 every six months starting immediately and continuing through four years from the present, and $100 every six months thereafter through ten years from the present, if ;(2) = 0.1. Answer = $ (round your answer to 2 decimal places.)