$\mathrm{}$A motorbike is travelling along a flat highway west to east with a constant velocity of 22$\mathrm{}\mathrm{}$m/$/$s.$.$  An HGV is travelling along the same highway, in the opposite direction with a constant velocity of $12$ m/$/$s.$.$  

 

a.$.$ If the vehicles collide, become entangled and continue together calculate their velocity after the collision.

b. The mass of the motorbike is 56$56$ kg,$,$ and the HGV is $1250$ kg.$$ What is the change in kinetic energy of the system?