searching groups of items and returning the one with the highest value in each group

how do I search groups of work orders and return the work order number that took the longest to complete.  The attached example shows 3 groups of work orders (each group is circled in red). The contractor is graded on the performance of each group of work orders.  For example, unit 7707PAT has 8 work orders.  All work orders within that group are judged based on the work order than takes the longest to complete (Calculated Hours - column P)  two of the work orders took 5 hours, so I would want to somehow isolate or extract either one of those work orders plus the two work orders highlighted below the first two (cells P11 & P19).  So in effect, the attachment indicates that there on only three work orders that I want to evaluate (I am only showing 3 out of hundreds of thousands).  The contractors bonus is based on what percent of the work orders are completed within a certain number of hours. I have been working on this for weeks and I am stumped.  Thanks in advance.

jimmy