$R_{ab}=(R_{3} // R_{4})+R_{2}+R_{1}=65$$U_{a,b}= I_{ab}.(R_{3,4}+R_{1}+R_{2}) = 90 (R_{3,4}=R_{3}//R_{4})$$I_{1}= I_{2}= I_{a,b}=3 $$I_{3}=I_{4}=6/5$
$R_{ab}=(R_{3} // R_{4})+R_{2}+R_{1}=65$$U_{a,b}= I_{ab}.(R_{3,4}+R_{1}+R_{2}) = 90 (R_{3,4}=R_{3}//R_{4})$$I_{1}=I_{2}=I_{ab}=3$$I_{3}=I_{4}=6/5$