A photojournalists flash unit uses a 9.0-V battery pack to charge a 0.15-F capacitor, which is then

A photojournalist’s flash unit uses a 9.0-V battery pack to charge a 0.15-μF capacitor, which is then discharged through the flash lamp of 10.5-Ω resistance when a switch is closed. The minimum voltage necessary for the flash discharge is 7.0 V. The capacitor is charged through a 18-kΩ resistor.

(a) How much time is required to charge the capacitor to the required 7.0 V?

(b) How much energy is released when the lamp flashes?

(c) How much energy is supplied by the battery during the charging cycle and what fraction of that energy is dissipated in the resistor?