Count Value of Cells that meet a certain condition

Hi all,

I have a spreadsheet whereby I track the contracted hours of staff as well as whether that person will be in the office in any given week or not. Team members changes periodically as not two teams are the same size.

Im looking to see if there is a way that I can calculate the total combined hours of any team (despite any further changes) as well as checking how that number differs over the week.

I have attached a spreadsheet here and whislt I have not yet had a go any any formulas on it, I have added notes to the table (see the table with borders) with explanations of what I'd like. I appreciate that this explanation may not be clear but I really do appreciate any help

Thank you!