Answer
$U_2=1.11\times10^-2J$
Work Step by Step
$U=\frac{1}{2}CV^2$
For capacitor 2, this simplifies to:
$U_2=\frac{1}{2}C_2V_2^2$
Thus, we plug in the known values to obtain:
$U_2=\frac{1}{2}(5\times10^{-6})(66.7)^2$
$U_2=1.11\times10^-2J$