In a chemistry lab, a solution is prepared by mixing two chemicals, X and Y, along with water. The volume of water in the mixture accounts for 25% of the total solution volume, while the volumes of chemicals X and Y are in the ratio 8 : 7. To separate water from the mixture, it is passed through a specialised filter that absorbs the water completely and partially absorbs chemical Y. This filter absorbs 180 ml of the original mixture. As a result, the volume ratio of chemicals X and Y in the remaining concentrated solution becomes 4 : 3. Calculate the volume of chemical Y absorbed by the filter.