Which of the following exhibits moderate electrical conductivity?

$A$ rope of mass $5\,kg$ is moving vertically in a vertical position with an upwards force of $100\,N$ acting at the upper end and a downwards force of $70\,N$ acting at the lower end. The tension at the midpoint of the rope is $............\,N$.

Two concentric coils of $10$ turns each are placed in the same plane. Their radii are $20 \ cm$ and $40 \ cm$ and carry $0.2 \ A$ and $0.3 \ A$ current respectively in opposite directions. The magnetic induction (in $T$) at the centre is

If,in a $\triangle ABC$,$\tan \frac{A}{2} = \frac{5}{6}$ and $\tan \frac{C}{2} = \frac{2}{5}$,then $a, b, c$ are such that :

Identify phenacetin from the following.

If the foot of the perpendicular from $(0,0,0)$ to a plane is $(1,2,3)$,then the equation of the plane is