Two particles each of mass $m$ and travelling with velocities $u_1$ and $u_2$ collide perfectly inelastically. The loss of energy will be
(a) $\frac{1}{4} m\left(u_1-u_2\right)^2$
(b) $\frac{1}{2} m\left(u_1-u_2\right)^2$
(c) $2 m\left(u_1-u_2\right)^2$
(d) $m\left(\mathrm{u}_1-u_2\right)^2$