Solution:
DPD= OP-TP
OP= Osmotic pressure
TP= Turgor pressure
DPD of cell P= 20-10=10atm
DPD of cell Q= 10-5= 5atm
Water always flows from lower DPD to higher DPD. In this case cell Q has lower DPD as compared to cell P. Therefore, water will flow from cell Q to cell P.