Question

The volumetric flow rate (per unit depth) between two streamlines having stream functions $\Psi _{1} ,  \Psi _{2}$   is                                               

           (a) $\left | \Psi + \Psi \right |$                                                    (b) $\Psi _{1} \Psi _{2}$         

            (c) $\Psi_{1} / \Psi _{2}$                                                               (d) $\left | \Psi - \Psi \right |$