Formula to calculate the percentage of work completed

[Zodiark]

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.