Ch$23$ Series$/$Parallel Circuits: Two resistors with resistances of $15\mathrm{.}0$ and $30\mathrm{.}0$ are connected in parallel. A $20\mathrm{.}0-$ resistor is then connected in series with this parallel combination. An ideal $9\mathrm{.}0-V$ battery is then connected across the seriesparallel combination. What is the current through $($a$)$ the $20\mathrm{.}0-$ resistor and $($b$)$ the $15\mathrm{.}0-$ resistor?