The collision is a form of inelastic collision because the it forms a single mass after is collides. So it can be solve by momentum balance
( 0.08 kg * 50 m/s ) + ( 0.06 kg * 50 m/s) = ( 0.08 + 0.06 kg ) v
V = 50 m/s
So the kinetic energy lost is
KE = 0.5 (50 m/s)^2) *( 0.14 – 0.08kg )
KE = 75 J