Power of sound from a very small loud speaker is $25 \mathrm{MW}.$ Sound level at a point which is at a distance $r$ from the speaker is $I_1.$ If power of loud speaker is increased to $1000 \mathrm{MW},$ then sound level at a point $2$ raway from the loud speaker is $I_2.$ Value of $I_2-I_1$ is $n \mathrm{dB}.$ Value of $n,$ is

A rod of mass $1.5 \mathrm{kg}$ and length $40 \mathrm{cm}$ is clamped with the help of two identical strings at the two ends as shown. A block of mass $5 \mathrm{kg}$ has to be connected on the rod. What should be the distance (in $\mathrm{cm}$ ) of point of suspension of block from the first end so that same tuning fork can vibrate the first string in second harmonic and the second string in third harmonic? $\left(g=10 \mathrm{m} {\mathrm{s}}^{-2}\right)$