$8\mathrm{.}8$ Consider a random process $x(t)$ defined by a finite sized ensemble consisting of four equally probable sample functions given by

$x_1(t)=-2u(t)$

$x_2(t)=cos5tu(t)$

$x_3(t)=u(t)$

$x_4(t)=2sin(6t+0\mathrm{.}2)u(t)$