a) I=E/(R+r)
R1=9 ohm => I1=E/(R1+r)=60/(9+1)=6 A
R2=9 ohm => I2=E/(R1+r)=60/(19+1)=3 A
R3=9 ohm => I3=E/(R1+r)=60/(29+1)=2 A
R4=9 ohm => I4=E/(R1+r)=60/39+1)=1,5 A
b) R=0 (se numeste scurtcircuit)
R0=0 ohm => I0=E/(R0+r)=60/(0+1)=60 A (curentul la scurtcircuit)