Thanks for the help!
1) It seems a little silly to write down so many decimal places when you know already that you don't get to keep any of them.
Are you SURE this presentation will go well on an examination? This is NOT how one would do it on a slide rule.
2) Do you have rounding rules?
Should it be 2.856 x 10^7 or 2.857 x 10^7?