Calculate the vorticity vector as a function of space variables $(x,y,z).$

$4-85$ A steady, two$-$dimensional velocity field is given by

vec$(V)=(u,v)$

$=(2\mathrm{.}85+1\mathrm{.}26x-0\mathrm{.}896y)vec(i)$

$+(3\mathrm{.}45x+cx-1\mathrm{.}26y)vec(j)$

Calculate constant $c$ such that the flow field is irrotational.Pls help me w it