A siphon is used to drain water from a large tank as shown in the figure below. Assume that the level of water is maintained constant. Ignore frictional effect due to viscosity and losses at entry and exit. At the exit of the siphon, the velocity of water is
(a) $\sqrt{2g\left ( Z_{Q}-Z_{R} \right )}$ 
(b) $\sqrt{2g\left ( Z_{P}-Z_{R} \right )}$ 
(c) $\sqrt{2g\left ( Z_{0}-Z_{R} \right )}$
(d)$\sqrt{2gZ_{Q}}$ 