Two charges are placed between the plates of a parallel plate capacitor. One charge is +q1 and the other is q2 = +7.21C. The charge per unit area on each plate has a magnitude of = 3.70 x 10-5 C/m2. The force on q1 due to q2 equals the force on q1 due to the electric field of the parallel plate capacitor. What is the distance r between the two charges?