The daily requirements of water of three families in our three-storyed flat are 1200 litres, 1050 litres and 950 litres respectively. After fulfilling these requirements in order to put up a tank again and to deposit to store 25% of the required water, only a land having the length of 2·5 m and breadth of 1 ·6 m has been procured. Calculate the depth of the tank in metre that should be made.