When a soap bubble is left in a room, air molecules diffuse out from the bubble. If at an instant, the concentrations of air molecules inside the bubble and in room are n; and no respectively and thickness of the walls of the bubble is h, the rate q of diffusion i.e. number of air molecules coming out of the bubble per second from a unit surface area is given by the following equation. 9=D ni - n h 0 Here D is a positive constant. If initial radius of the bubble is ro and initial thickness of the walls of the bubble is ho, find expression for rate of change in radius r of the bubble. Atmospheric pressure in the room is Po and surface tension of the soap solution is o. Neglect evaporation of soap solution and treat air as an ideal gas.