a$)(10$ points$)$ Two identical balls collide head on$.$ Ball A is moving at $75\mathrm{.}0$ cm$/$s east while Ball B is moving at $43\mathrm{.}0$ cm$/$s west. If the collision is perfectly elastic, what is the velocity of each ball after the collision?

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$$b$)$ A satellite orbits the Earth at an altitude of $200$ km $(2\mathrm{.}00$ x $102$ km$).$What is the speed of the satellite?