Date and time manipulations

[Rune Mossige <r mossige sensewave com>]

Hello,
I have a very simple time-sheet that I have started on, with simple entries
like:

Date       Start-time   End-time  Time-spent
17/3/2002  16:30        17:45     1:15

I get correct entries for the time-spent when I do (End-time-Start-time), and
I also get correct, apparently, when I do a sum of the Time-spent to figure
out the total number of hours entered.

However, once I have got my total number of hours, I want to calculate a cost
for these hours, e.g. I have adde up 27 hours 15 minutes (27:15), and have a
monetary amount, e.g. US$ 995.40, and I want to arrive at a monetary value,
US$ XXX per hour...how do I get to this number easiest?

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