LKS, your diagram shows a bypass line around the pump.
Perhaps it is meant to represent internal recirculation, which occurs in some types of pumps, or perhaps it is meant to represent an external bypass line, sometimes used on centrifugal pumps to move the operating point of the pump for a couple of reasons, and which may be equipped with a control valve, not shown, or sized to control the flow naturally just by its geometry.
Also, points A and B both seem to refer to tee junctions, which in general have three associated flows, and it's not clear to which flow each of the letters refer.
We here could be more helpful to you if you provide a little background about your education level, experience level, and exactly what problems you are trying to solve. If you take some time to browse the site, you will notice that the best and most useful answers arrive most quickly in response to fairly detailed questions that provide answers to the first ten obvious questions that can be conjectured.
Thank you for your cooperation, and good luck.
Mike Halloran
Pembroke Pines, FL, USA