An electric dipole of dipole moment $2.0 \times 10^{-8}\ \text{C m}$ is held in a uniform electric field of $5.0 \times 10^{4}\ \text{N/C}$, with its dipole moment at $60^\circ$ to the field. How much work must an outside agent do to turn the dipole slowly until its moment points exactly opposite to the field?