On a very muddy football field, a defender with a mass of $110$ kg is stopping a midfielder with a mass of $90$ kg$.$ Just before the collision, the defender is running north at a speed of $21\mathrm{.}6$ km$/$h$,$ while the midfielder is running towards the east at a speed of $7\mathrm{.}2$ m$/$s$.$ According to Buns; 

a$\mathrm{) }$What will be the magnitude and direction of the joint velocities of these two players after impact?

b$\mathrm{ ) }$Calculate the kinetic energy of the football players before impact. 

c$\mathrm{) }$Calculate the kinetic energies of the football players after impact.