Помогите решить схему по физике

R123=R1+R2+R3=5+4+3=12 Ом;
R1234=(R123*R4)/(R123+R4)=(12*6)/(12+6)=72/18=4 Ом;
Rобщ.=R1234+R5=4+2=6 Ом;

I123=I1=I2=I3=4 A;

U123=U1+U2+U3;
U1=R1*I1=5*4=20 B;
U2=R2*I2=4*4=16 B;
U3=R3*I3=3*4=12 B;
U123=20+16+12=48 B;

U1234=U123=U4=48 B;

I1234=I123+I4=4+(48/6)=4+8=12 A;

Iобщ.=I1234=I5=12 A;

U общ.=U1234+U5=48+(12*2)=48+24=72 B;