A molecule of a substance has permanent dipole moment p. A mole of this substance is polarised by applying a strong electrostatic field E. The direction of the field is suddenly changed by an angle of $$60^\circ$$. If N is the Avogadro's number the amount of work done by the field is :

A

2 NPE

B

$$\frac{1}{2}$$ NPE

C

NPE

D

$$\frac{3}{2}$$ NPE