Construct and run the following MATLAB code:

x$=$randn$(1000,1)$;

figure$(1),$spec analysis$($x$,1)$

h$=$fir$1(30,0\mathrm{.}2*2)$;

y$=$filter$($h$,1,$x$)$;

figure$(2),$spec analysis$($y$,1)$

$($a$)$ Explain what does each line of the code perform.

$($b$)$ By running the code, observe and explain the results.