A series LCR circuit with $R=20 \Omega, L=1.6 \mathrm{H}$ and $C=40 \mu \mathrm{~F}$ is connected to a variable frequency a.c. source. The inductive reactance at resonant frequency is $\_\_\_\_$ $\Omega$.

When an external resistance of $5 \Omega$ is connected across terminals of a cell, a current of 0.25 A flows through it. When the $5 \Omega$ resistor is replaced by a $2 \Omega$ resistor, a current of 0.5 A flows through it. The internal resistance of the cell is $\_\_\_\_$ $\Omega$.

A circular loop of radius 20 cm and resistance $2 \Omega$ is placed in a time varying magnetic field $\vec{B}=\left(2 t^2+2 t+3\right) T$. At $t=0$, for the plane of the loop being perpendicular to the magnetic field and, the induced current in the loop at $t=3 \mathrm{~s}$ is $\frac{\alpha}{50} \mathrm{~A}$. The value of $\alpha$ is $\_\_\_\_$ . (Take $\pi=22 / 7$ )