d
Frequency of tunning fork $=\mathrm{N}$
Sonometer wire is either $\mathrm{N}+\mathrm{S}$ or $\mathrm{N}-\mathrm{S}$
$\mathrm{n} \propto \frac{1}{\ell} \quad \frac{\mathrm{n}_{1}}{\mathrm{n}_{2}}=\frac{\ell_{2}}{\ell_{1}}$
$\frac{N+5}{N-5}=\frac{1.05}{1}$
$\mathrm{N}=205 \mathrm{\,Hz}$