$[3]-10$ points $-$ Give a short answer for the following questions$($MATLAB$)$:

$($a$)$ What is wrong with this while loop?

$x=sin()$;$y=2$;

while $x>0$

$z=x+y$;

end

$($b$)$ After how many cycles will this for$-$loop end?

$x=1$;$y=2$;

for $i=1$:$2$:$50$

for $i=1$:$2$:$50$

$z=x+y$;

end