Here is the model answer, for full marks:Since we are referring to India, CADR 220 means the air purifier cleans 220 m3 of air per hour.Room areas that could be cleared by this air purifier will be different based on the types of rooms.Using table 1, here are the areas you can clean for various types of rooms:537 ft2: Bedrooms269 ft2: Hospital rooms, offices, school classrooms, waiting rooms, banks179 ft2: Living rooms, hair and beauty salons, shops154 ft2: Kitchens in homes133 ft2: Foyers, conference rooms, clinics, restaurants89 ft2: Dining halls, club rooms72 ft2: Restaurant kitchens, smoking rooms53 ft2: Bars and discothequesThese are the room areas that an air purifier with CADR 220 m3/hr can clean to extremely pristine levels, with almost no pollution left.Some experts recommend using such an air purifier for 25% lesser area than the calculated values above. This is to provide a margin of safety for errors in judging room dimensions and dynamics.So, our purifier will clean an average room space of 268 ft2 to an excellent level.These calculations assume the ceiling is 9 ft in height. If it is lower than this, you can increase the area covered proportionately.This answer should fetch you full marks. :-)