An electric dipole of dipole moment is $6.0 \times 10^{-6} \mathrm{Cm}$ placed in a uniform electric field of $1.5 \times 10^3 \mathrm{NC}^{-1}$ in such a way that dipole moment is along electric field. The work done in rotating dipole by $180^{\circ}$ in this field will be $\_\_\_\_$ mJ
