How to calculate working days including time in SQL Server 2005

To simplify for the various time zones, we are going to use GMT time to determine when the weekend starts and ends.

Weekend will start on Saturday 00:00 GMT and end on Monday 00:00 GMT, regardless of what OU/time zone the user is working from.

So taking the example above, instead of taking 2.75 days for the E2E cycle time, it would be .75 days, as it would be 8 hours on Friday + 10 hours on Monday = 18 hours (or .75 days)

How do I calculate this in SQL Server?