A person decided to use his bath tub water to generate electric power to run a 40W bulb. The bath tub is located at a height of h meters from ground and it holds V litres of water. He installs a water driven wheel generator on ground. The rate in m3/s at which water should drain from bath tub to light the bulb, if efficiency of machine be 90%, is (Given density of water =ρ and acceleration due to gravity =g)