Answer:
The answer is CHP+IHP.
Explanation:
Capillary hydrostatic pressure (CHP) works toward interstitial fluid and  interstitial hydrostatic pressure (IHP) works toward capillary. Net filtration pressure for the filtration and reabsorption is obtained from the resultant force between CHP and IHP
Mathematically it is the sum of CHP and IHP. For filtration net hydrostatic pressure value is positive( i.e CHP+IHP = positive value), but for reabsorption net hydrostatic pressure is negative( CHP+IHP =negative value).
So the answer is CHP+IHP.
