A cannon fires successively two shells with speed 10 m/s, the first at an angle ${60}^{\circ }$and the second at an angle ${45}^{\circ }$to the horizontal in same plane. Find horizontal distance where firing leads to collision of shells  $(\mathrm{take}\mathrm{g}=10\mathrm{m}/{\mathrm{s}}^2\mathrm{and} \sqrt{3}=1.7)$