The frequency of a sonometer wire is $$100 \mathrm{~Hz}$$ When the weights producing the tensions are completely immersed in water, the frequence becomes $$60 \mathrm{~Hz}$$ and on immersing the weights in a certain liquid, the frequency becomes $$40 \mathrm{~Hz}$$. The specific gravity of the liquid is

A man stands between two parallel cliffs (not in middle). When he claps his hands, he hears two echoes one after is and the other after $$2 \mathrm{~s}$$. If the velocity of sound in air is $$330 \mathrm{~m} / \mathrm{s}$$, the width of the cliff is