Suppose that, after a particular step of $A\frac{5}{1}$ stream cipher, the values in the registers are:

$x=(x_0,x_1,$dots,$x_{18})=(1010101010101010110)$

$Y=(y_0,y_1,$dots,$y_{21})=(1100110001101100010011)$

$Z=(z_0,z_1,$dots,$z_{22})=(11100101110000011000011)$

a$)$ List the next $4$ keystream bits.

b$)$ Give the contents of $x,Y,$ and $Z$ after the generation of each of these $4$ bits.