Answer
a) $I_{rms}=4.47A$
and $I_{peak}=6.32A$
b) $V_{rms}=112V$
and $V_{peak}=158V$
Work Step by Step
a) $P_{avg}=I_{rms}^{2}R$
or, $500=I_{rms}^{2}\times25$
or, $I_{rms}=4.47A$
So, $I_{peak}=\sqrt 2\times 4.47=6.32A$
b) $V_{rms}=4.47\times 25=112V$
and $V_{peak}=\sqrt 2\times112=158V$