c$.$ Does a velocity potential exist for the flow given in $($b$)?$ If so$,$ find it$.$

$($Bonus $10\%)$ The velocity potential for a steady, incompressible, $2$ D inviscid flow is given by $=2x^{2}y-\frac{2}{3}{y}^3$ Does a stream function exist for the given flow? If so$,$ find it$.$

Bonus $10\%)$ The velocity potential for a steady, incompressible, $2$D inviscid flow is given by $=2x^{2}y-\frac{2}{3}{y}^3.$ oes a stream function exist for the given flow? If so$,$ find it$.$