Need Help

Need Help

I am trying to create a chart or graph to measure employee efficiency.  I'm trying to measure the average hours per employee per a certain task.   In the timesheet data (table) I have the following information as an example:

Employee 1  Project A  hours x  Title/Task C
Employee 1  Project A  hours y  Title/Task C
Employee 1  Project A  hours z  Title/Task C
Employee 1  Project B  hours q  Title/Task C
Employee 1  Project B  hours r   Title/Task C
Employee 1  Project B  hours s  Title/Task C


So the calculation I am after is as follows:  (x+y+z) + (q+r+s)/2

2 represents the distinct number of projects.  

I made an attempt using the following formula, but I get an error saying specified formula is invalid.

sum( "Timesheets"."Hours")/count(distinct( "Timesheets"."Project Name")


Any help or work arounds???