6-3

a)
I=\frac{U}{R}=\frac{12V}{10{,}0\Omega}=1{,}2A
b)
I=\frac{U}{R}=\frac{12V}{2{,}5\Omega}=4{,}8A
R_{kok}=\frac{5{,}0^2}{5{,}0+5{,}0}=2{,}5\Omega