24.21 For the system of capacitors shown in Fig. E24.21, a potential difference of 25 V is maintained across ab. (a) What is the equivalent capacitance of this system between a and b? (b) How much charge is stored by this system? (c) How much charge does the 6.5 nF capacitor store? (d) What is the potential difference across the 7.5-nF capacitor? Figure E24.21 7.5 nF 18.0 nF 30.0 nF 10.0 nF 6.5 nF