Explanation

(a) Here ,$T_{1} = 16\ N,\ T_{2} = ?$
As per the choice given, $T_{2} > T_{1}$
$\ \ \therefore n_{2} > n_{1},\ \left( n_{2} - n_{1} \right) = 3\ \ \ \ \ \ \ \ \ \ldots(i)$
As $n \propto \sqrt{T}$
$\therefore\ \ \frac{n_{2}}{n_{1}} = \sqrt{\frac{T}{16}} = \sqrt{\frac{T}{4}}$
If $n_{1}$ corresponds to $4:n_{2}$ corresponds to $3 + 4 = 7$, which is $\sqrt{T}$. Therefore, $T = 49\ N$