How can I retrieve target working hours via the API?

I need the scheduled capacity of certain team in a fixed period (in my case a sprint of 2 weeks).
The only approach I see:

getEmployement (to get the team, employmnet_start_date, termination and weekly_working_hours)
getAbsencePeriods and Absence Period Breakdowns

With this information + the external information about weekday-holidays I can calculate exact values for all persons working 5 days a week. (for 2 weeks: 2 weekly_working_hours - (absence days + holidays) weekly_working_hours / 5)

But I find no way to handle employees who work only 3 or 4 days a week correctly as i would need to know on wich days they work in order to calculate the impact of public holidays.