$12\mathrm{.}3$ The binary exponential backoff algorithm is defined by IEEE $802$ as follows:

The delay is an integral multiple of slot time. The number of slot times to delay

before the $n$th retransmission attempt is chosen as a uniformly distributed random

integer $r$ in the range where $K=$min$(n,10).$

Slot time is$,$ roughly, twice the round$-$trip propagation delay. Assume that two sta$-$

tions always have a frame to send. After a collision, what is the mean number of

retransmission attempts before one station successfully retransmits? What is the

answer if three stations always have frames to send?