Answer
$J = 1.32\times 10^7~A/m^2$
Work Step by Step
We can find the equivalent resistance:
$R_{eq} = 0.127~\Omega+0.729~\Omega = 0.856~\Omega$
We can find the current:
$i = \frac{60.0~V}{0.856~\Omega} = 70.09~A$
We can find the current density:
$J = \frac{current}{area}$
$J = \frac{i}{\pi~r^2}$
$J = \frac{70.09~A}{(\pi)~(1.30\times 10^{-3}~m)^2}$
$J = 1.32\times 10^7~A/m^2$
