If you can only do $1$ do C please.

Prove the validity of the following total$-$correctness sequents:

a$.|--{?}_{\text{t}\text{o}\text{t}}(|x0|)$ Copy$1(|x=y|)$

b$.|--{?}_{\text{t}\text{o}\text{t}}(|y0|)$ Multi$1(|$z$=$x$*$y$|)$

c$.|--{?}_{\text{t}\text{o}\text{t}}(|(y=y_0{)}^{{?}^{?}}(y0)|)$ Multi$2(|z=x*y_0)$

Copy$1$

$a=0$;

$z=0$;

while $(ay)\{$

$,z=z+x$

$,a=a+1$

$\}$