What is the figure given below showing in particular?

$A$ $TV$ transmitter has a range of $50 \ km$. The height of the $TV$ transmitter is . . . . . . (Radius of the earth,$R_e = 6.4 \times 10^6 \ m$). (in $m$)

Which one of the following plots is correct for a first order reaction?

The normal freezing point $(f.p.)$ of nitrobenzene is $278.82\, K$. If a non-volatile solute is dissolved in it and a solution of $0.25\, m$ (molality) is prepared,the observed $f.p.$ of the solution is $276.82\, K$. Evaluate $K_f$ of nitrobenzene in $K\, kg\, mol^{-1}$.

The maximum value of $ \left(\frac{1}{x}\right)^{x} $ is

$A$ plane passing through $(-1, 2, 3)$ and whose normal makes equal angles with the coordinate axes is