$13-$ A $100$ milli F capacitor is connecteri in series with a $10\mathrm{.}00$ resistor. This combination is connected in parallel with a $25\mathrm{.}0$ resistor. The whole circuit $($both branches$)$ are then connected across a $45$ V battery that cari be switched on and off. The capacitor starts off fully discharged.

a$)$ draw the circuit.

b$)$ If the battery is removed after the capacitor is fully charged, how long will it take for the voltage to drop to $20\%$ of its original value.

$10\%$