The dipole moment of water molecule is `6.3 xx 10^-30 Cm`. A sample of water contains 1021 molecules, whose dipole moments are all oriented in an electric field of strength `2.5 xx 10^5 N//C`. Calculate the work to be done to rotate the dipoles from their initial orientation `theta_1` = 0 to one in which all the dipoles are perpendicular to the field, `theta_2 = 90^@`.