Lightning as a crude model for lightning, consider the ground to be one plate of a parallel-plate capacitor and a cloud at an altitude of 650 m to be the other plate. assume the surface area of the cloud to be the same as the area of a square that is 0.70 km on a side. a. what is the capacitance of this capacitor? b. how much charge can the cloud hold before the dielectric strength of the air is exceeded and a spark (lightning) results?