Formula to Account for Weekend Days for an SLA

Hi, I need some help trying to figure out the best way to calculate the weekend days for a service level agreement. It's for a radiology center. The center has an SLA with radiologists to interpret images within 1 business day from the date the images are uploaded to the radiology system. Many of these radiologists work on the weekends. Sometimes they will get images uploaded on a Friday and will interpret on the weekend. Or, images uploaded on Saturday or Sunday and interpreted on Monday or Tuesday. An image uploaded on a Friday or Saturday but interpreted on a Monday is still 1 business day. Then there are federal holidays to take into account but I can put that aside if it's too complicated. I need a formula that will subtract the days of the weekend but I'm not sure how to go about it. I attached an example of the spreadsheet and would appreciate some input.