II A lottery machine uses blowing air to keep $2000$ Ping$-$Pong balls bouncing around inside a $1\mathrm{.}0m1\mathrm{.}0m1\mathrm{.}0m$ box. The diameter of a PingPong ball is $3\mathrm{.}0cm.$ What is the mean free path between collisions? Give your answer in $cm.$