Determine the change in volume of 6 litres of alcohol if the pressure is decreased from 200 cm of Hg to 75 cm. [velocity of sound in alcohol us 1280 m/s, density of alcohol = 0.81 gm/c c, density of Hg `- 13.6 gm//c c` and `g = 9.81 m//s^(2)`]