Overtime calculation

We are currently developing our time tracking which will be an individual board for each employee. We track time on cost centers for our accounting, not the actual project. Each group is one month (see the image). We would like to take the sum of all hours from one month and check it against the expected working hours of this month. Is there a way to A) refer to the column overview or do I need to calculate the sum of the column within the formula and B) is it possible to write a formula that checks the month and its working days to multiply this by the working hours per working day?

I appreciate your help!
Best,
Philip