MULTIPLE ACCESS PROTOCOLS: COLLISIONS

Consider the figure below, which shows the arrival of $12$ messages for transmission at different multiple access wireless nodes at times

$t=($:$0\mathrm{.}5,0\mathrm{.}6,0\mathrm{.}8,1\mathrm{.}2,1\mathrm{.}8,2\mathrm{.}2,2\mathrm{.}3,3\mathrm{.}2,3\mathrm{.}4,3\mathrm{.}5,4\mathrm{.}4,4\mathrm{.}9$:$)$ and each transmission requires exactly one time unit.