In a closed organ pipe, the frequency of fundamental note is $30 \mathrm{Hz}$. A certain amount of water is now poured in the organ pipe so that the fundamental frequency is increased to $110 \mathrm{Hz}$. If the organ pipe has a cross-sectional area of $2 {\mathrm{cm}}^2$, the amount of water poured in the organ tube is ________$\mathrm{g}$. (Take speed of sound in air is $330 \mathrm{m} {\mathrm{s}}^{-1}$ )