The energy stored in a capacitor is given by:
[tex] U=\frac{1}{2}CV^2 [/tex]
where C is the capacitance and V is the potential difference applied across the capacitor.
In this problem, we have:
[tex] C=3000 \mu F= 3000 \cdot 10^{-6} F [/tex]
[tex] V=87.0 V [/tex]
Substituting the numbers into the equation, we find the energy stored:
[tex] U=\frac{1}{2}(3000 \cdot 10^{-6} F)(87 V)^2=11.4 J [/tex]
