BSC has the error probability p $=0\mathrm{.}2$ and the input to the channel consists of $4$ equiprobable

Messages x$1=000$; x$2=001$; x$3=011$; x$4=111.$ Calculate

$($a$)$ P$(0)$ and p $(1)$ at the input;

$($b$)$ Efficiency of the code;

$($c$)$ Channel capacity.