v1=10;
v2=20;
r1=10^3;
r2=2*10^3;
r3=3*10^3;
r4=4*10^3;
r5=5*10^3;
i2=(v*(r1+r2)-v1*r2)/((r2+r3+r5)*(r1+r2)-r2^2);
vth=v2-i2*r5;
rth=(r1*r2/(r1+r2)+r3)*r5/(r1*r2/(r1+r2)+r3+r5);
i=vth/(rth+r4);
disp("the current (in mA) in R4 is"); disp(i*10^3);