Use Bernoulli's equation

The diameters D&d piped, Venturimeter like horizontal water flow sistem seen in the drawing is connected to a piston - cylinder system of Dp piston and dp rod diameter and connected to the incoming flow pipe and the contracted cross section. Assuming that the ideal - no head loss flow conditions are valid; Calculate the force F applied to the piston when the average velocity and the pressure at the entrance cross-section is V and p respectively. p=4,5[bar],v=5[m/s] D=10[mm],d=5[mm]&Dp=30[mm],dp=6[mm]