An amount of charge ±Q is placed on the plates of a parallel-plate capacitor so that the potential across the plates is ΔV_init. The capacitor is then disconnected, and the separation between its plates is increased by a factor of three. If the charge on the plates is ±35 µC while the final capacitance is 2.0 × 10^-9 F, what was ΔV_init?