A parallel-plate capacitor in which the plates are extendable is connected to a battery and charged until there is a charge \(+q\) on one plate and a charge \(-q\) on the other plate.

(a) With the battery still connected, the area of each plate is doubled by sliding the extension out. How much charge is on each plate now?

(b) In which case, before the plate area is expanded or after, is more force required to keep the plates apart? Use the elastic-band model described in Problem 69 to explain your answer.