A cylindrical tank is placed with its axis vertical. A circular orifice of 40 mm diameter is fitted at its bottom. The supply of water into the tank is at uniform rate and at the same time water is discharged through the orifice. A manometer tube is fitted on the side of the tank to indicate the level of the water. An observer starts the stop watch when water level was at 600 mm. It was found that water level becomes 800 mm after one minute. Again the observer starts the stop watch when water level was at 1 m and it was found that water level becomes 1.1 m in one minute. Calculate the diameter of the tank by assuming coefficient of discharge for the orifice equal to 0.6.