counting and grouping in sql based on a values

Hi experts need to amend the code I have to cater for one more thing and I am really stuck as to how to proceed - so im hoping someone can help me

I have attached a spreadsheet which shows the classes that one student attended for one day and also the marks made against that student for the one day.

In the code below I am calculating the time_absent where attendance_type = 'AA' or 'AB' but I need to change this to calculate the time_absent based on each different descriptions in the description field (shown in spreadsheet).  Using the example from the spreadsheet I need two different descriptions being authorised absence and class cancelled and I need a seperate line for each description.  

Help Appreciated example-output.xls

SELECT acad_period, student_id, student_name, student_surname, stage_code,
	course_code, course_period, course_desc, dept_code, dept_desc,
	campus_id, campus_desc,
	date, week_no, [start_time], [end_time], 
	convert(varchar, convert(int,floor([Total Hours])))+':'+
	replicate('0',(2 - len(convert (varchar, convert(int,([Total Hours] - floor([Total Hours])) * 60.0)))))
	+convert (varchar, convert(int,([Total Hours] - floor([Total Hours])) * 60.0)) as total_hours,
	(CASE WHEN [total breaks]  < 0 THEN '-' ELSE '' END) + convert(varchar, convert(int,ABS([total breaks] -([total breaks] %1))))+':'+ 
	RIGHT(('0'+convert(varchar,  convert(int,60*ABS([total breaks] %1)))),2) as total_breaks,
	CONVERT(VARCHAR(5), [Late], 108) AS late,
	CONVERT(VARCHAR(5), [Absent], 108) AS time_absent,
	CONVERT(VARCHAR(5), [Unmarked], 108) AS not_marked,
	CONVERT(VARCHAR(5), [Present], 108) AS time_present

FROM
(
	SELECT  acad_period, student_id, student_name, student_surname, stage_code,
		course_code, course_period, course_desc, dept_code, dept_desc,
		campus_id, campus_desc, 
		Date,week_no, 
		MIN(CONVERT(datetime, start_time)) AS 'start_time', 
		MAX(CONVERT(datetime, End_Time)) AS 'end_time',
		ROUND(cast((datediff(mi, MIN(start_time), MAX(end_time))  / 60.0) as FLOAT),2) AS 'Total Hours',

		(DATEDIFF(minute, MIN(start_time), MAX(end_time)) - SUM(DATEDIFF(minute, start_time, end_time))) / 60.0 AS 'Total Breaks',
		
		DateAdd(n, SUM(CASE WHEN attendance_type = 'LA' THEN late_minutes ELSE 0 END), 0) AS 'Late',
		DateAdd(n, SUM(CASE WHEN attendance_type IN ('AA', 'AB') THEN DATEDIFF(minute, start_time,  end_time) ELSE 0 END), 0) AS 'Absent',
		DateAdd(n, SUM(CASE WHEN attendance_type IS NULL THEN DATEDIFF(minute, start_time,  end_time) ELSE 0 END), 0) AS 'Unmarked',
		DateAdd(n, SUM(CASE WHEN attendance_type IN ('PR', 'LA') THEN DATEDIFF(minute, start_time,  end_time) ELSE 0 END) 
			- SUM(CASE WHEN attendance_type = 'LA' THEN late_minutes ELSE 0 END), 0) AS 'Present'
	

	FROM stud_table
	GROUP BY acad_period, student_id, student_name, student_surname, stage_code,
	course_code, course_period, course_desc, dept_code, dept_desc,
	campus_id, campus_desc, Date, week_no
) X

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