Eaa=111;Ia=120;Ra=0.1;
Rfw=80;Eac=85;If=0.5;
v=100;

Vt=Eaa-(Ia*Ra)

Rf=v/1
 
Rfc=Rf-Rfw
 
Rfcrit=Eac/If
 
Rfc=Rfcrit-Rfw