Formula to calculate the percentage of work completed

I was given a problem by a friend of mine to see if I could figure it out. I can't. The problem is this:

A production line produces 280 cases in 1 hour. The workday lasts 12 hours. This totals to 3360 cases, at 100% of the daily quota. I need a formula that will show the percentage completed. For instance, after 6 hours, it should show 50% completed. I've uploaded my workbook, and thank you in advance.

In cell C3 type the formula

=B3/$B$7

copy the formula down

Thanks!

Thanks a bunch, it worked perfectly!
But now let's say that I wanted to be able to change the percentage by changing the data in Column A: such as if instead of having a consistent rate of production, I had varying amounts completed each hour? Is there a way for me to make the percentage based of of A?

You mean just to use the case produced?
In that case, just alter the formula to be
C3=A3/$A$7
copy the formula down