If forces of magnitudes 6 and 7 units acting in the directions 

 $\overline{\mathrm{i}} - 2 \overline{\mathrm{j}} + 2\overline{\mathrm{k}}$ and $2 \overline{\mathrm{i}} - 3 \overline{\mathrm{j}} - 6\overline{\mathrm{k}}$ respectively act on particle which is displaced   from P (2, -1, -3) to Q (5, -1, 1) then the work done by the forces is