A long circular tube of length 10 m and radius 0.3 carries a current I along its curved surface as shown. A wire-loop of resistance 0.005 ohm and of radius 0.1 m is placed inside the tube with its axis coinciding with the axis of the tube. The current varies as $$I = I_0 \cos(300 t)$$ where $$I_0$$ is constant. If the magnetic moment of the loop is $$N \mu_0 I_0 \sin(300 t)$$. then 'N' is.