$2.($a$)$ Two particles are created in a high$-$energy accelerator and move off in opposite directions. The speed of one particle, as measured in the laboratory, is $0\mathrm{.}650$c$,$ and the speed of each particle relative to the other is $0\mathrm{.}950$c$.$ What is the speed of the second particle, as measured in the laboratory? $(10$ pts$)($b$)$ The positive muon $($u$+),$ an unstable particle, lives on average $2\mathrm{.}20$ x $10-6$ s $($measured in its own frame of reference$)$ before decaying. $($i$)$ If such a particle is moving, with respect to the laboratory, with a speed of $0\mathrm{.}900$c$,$ what average lifetime is measured in the laboratory? $($ii$)$ What average distance, measured in the laboratory, does the particle move before decaying? $(15$ pts$)$