A parallel-plate capacitor has capacitance C = 12.4 pF when the volume between the plates is filled with air. The plates are circular, with radius 2.50 cm. The capacitor is connected to a battery and a charge of magnitude 30.0 pC goes into each plate. With the capacitor still connected to the battery, a slab of dielectric is inserted between the plates, completely filling the space between the plates. After the dielectric has been inserted, the charge on each plate has magnitude 45.0 pC. What is the dielectric constant K of the dielectric?