Capacitors...messed up first time?

An unknown number of identical capacitors, each having a capacitance of 8.00 mF are connected in parallel and then the combination is connected across the terminals of a battery with an EMF of 10.0 V. After the circuit reaches equilibrium and electrons no longer move out of the battery and into the capacitors, the amount of energy stored in the circuit is 6.40 J. How many capacitors are in the circuit?