Answer
$U=35 \mu J$
Work Step by Step
To find the work, use the equation for total energy in a capacitor, which is $$U=\frac{1}{2}CV^2$$ Substituting known values of $C=7.8 \mu F$ and $V=3.0V$ yields a work of $$U=\frac{1}{2}(7.8\mu F)(3.0V)^2=35 \mu J$$
