Sum Hours By Category And Then Group By Week Of

I need to sum the attendance hours by category and then group by 'Week of'. The 'Week of' start date is defined by the Monday in that week but Sunday is works too. If the Category Values are in ’Art’ or ‘PE’, they need to be combined into Non Educational. I also need to be able to flag the day(s) a student reaches 120 hours.

My table which is structured like this:

CREATE TABLE Attendance (
DOP_ID int,
Category varchar(20),
Title varchar(20),
Date datetime,
Hours int,
)

[Code] ....

I need an end result which looks like this:

ID Category Week of Total Hours
4504498 GED Program 7/1/2012 26
4504498 GED Program 7/8/2012 23
4504498 High School 7/1/2012 19
4504498 High School 7/8/2012 28
9201052 Non Educational 7/15/2012 30

ID Day_120_Hours_Reached
356485 6/30/2012
356485 11/15/2012
555666 10/12/2012
555666 2/25/2013

I have been looking for examples of a Week function that will pull out the 'week of' from a date using MS Sql Server and I can't find much info.