At what rate does the electric field change between the plates of a square capacitor of side 5 cm, if the plates are spaced 1.2 mm apart and the voltage across them is changing at a rate of 60 V?
a) 25,000 V/m²
b) 30,000 V/m²
c) 35,000 V/m²
d) 40,000 V/m²