Work done= Final gravitational potential -Initial gravitational potential
$\qquad=v_f -v_i =3\bigg[\bigg(\large\frac{-Gmm}{r_f}\bigg)-\bigg(\frac{-Gmm}{r_i}\bigg)\bigg]$
$ m= 0.1 \quad r_f=0.4\;m \quad r_i=0.2\; m$
Substituting these values we get
$W= 3\bigg[-Gmm \bigg(\large\frac{1}{.4}-\frac{1}{.2}\bigg)\bigg]$
$W= 5.0 \times 10^{-12}J$
Hence a is the correct answer.