A ball is moving in the x$-$direction at $5$ m$/$s and strikes another ball of the same mass of $2$ kg moving in the y$-$direction at $8$ m$/$s$.$ As a result of the collision, the first ball moves at $4$ m$/$s and the second ball moves at $7$m$/$s$.$ What is the change in kinetic energy of the system? answer is $-24$ J please be elaborative and direct in explanations$/$answer$,$ thank you!