Radius $r =0.5 \,mm =5 \times 10^{-4}\, m$

$E =10 \times 10^{-3}\, \frac{ V }{ m }$

$J =\sigma E =10 \times 10^{-3} \times 5 \times 10^{7}$

$J =5 \times 10^{5}$

$\frac{ i }{ A }=5 \times 10^{5}$

$i =5 \times 10^{5} \times \pi r ^{2}$

$=5 \times 10^{5} \times \pi \times\left(5 \times 10^{-4}\right)^{2}$

$=125 \pi \times 10^{-3} \,Amp$

$i=125 \pi \, mA$

$x=5$