Answer
$102\;\rm V$
Work Step by Step
According to Ohm’s law,
$$\Delta V=IR$$
where $R=\dfrac{\rho L}{A}$
$$\Delta V=I\dfrac{\rho L}{A}$$
$$\Delta V= \dfrac{\rho IL}{\pi r^2}$$
Plug the known to find the potential difference between the hands that is needed for a lethal shock of 100 mA across the chest.
$$\Delta V= \dfrac{(5)(100\times 10^{-3}) (1.6)}{\pi (5\times 10^{-2})}$$
$$\Delta V=\color{red}{\bf 102}\;\rm V$$