Answer
$V_{rms} = 224~V$
Work Step by Step
In part (a), we found that $I_{rms} = 2.59~A$
We can find the $rms$ voltage across $L$:
$V_{rms} = I_{rms}~X_L$
$V_{rms} = I_{rms}~2\pi~f_d~L$
$V_{rms} = (2.59~A)(2\pi)(550~Hz)(0.0250~H)$
$V_{rms} = 224~V$
