Ucd=-2ch33=-6(V), that is, the potential at point C is -6V.
Uad=Uac+Ucd=8-6=2(V), that is, the potential at point A is 2V.
Uba =-3+2i =-3+2×1=-1(v) or UBA =1× (-I) =/kloc-0 /× (-1) =-/kloc-.
Ubd = UBA+UAD =-1+2 =1(v), that is, the potential at point b is1v.