A hot wire instrument reads 15 A. The peak value of the current is

$15\sqrt 2A$ $\frac{15}{\sqrt 2}A$ $15\pi A$ $\frac{15}{\pi}A$

$15\sqrt 2A$

A hot wire instruments read RMS value. $\Rightarrow I_{rms} = 15A$ $\Rightarrow I_0 = I_{rms} \sqrt 2 = 15\sqrt 2 A$