sum 2 columns?

[nikko50]

I'm tryig to get the sum of total time spent on each activity worked by employees. Below is the sql I have but it does not sum. I need to sum hours and minutes to get a total amount of time spent on each ACTIVITY for a date range? How can I do this?

SELECT *,SUM(HOURS),SUM(MINUTES)
               FROM DAILY_ACTIVITY 
               WHERE  ACTIVITY_DATE  >= '2011-03-03'
                  AND ACTIVITY_DATE <= '2011-04-11'     

               AND HOURS + MINUTES > 0
              AND USERID  = '36'
GROUP BY ACTIVITY

[johanafm]

SUM(hours * 60 + minutes)