将计算重叠日期数组中的总小时数的公式

I've been trying to solve an issue for a while now and I'm just not getting the results I need. I have a spreadsheet that captures labor hours at a mechanic shop and I want to find out how many hours of labor per mechanic. The system uses open work-orders to calculate labor hours, however it allows for multiple work-orders to be open for one mechanic and the date/time of those work-orders often overlaps. I've been trying to solve an issue for a while