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You can either go for a 1 ton AC or a 1.5 ton AC depending upon the amount of light that enters the room, area and direction of windows, the floor on which your room is situated, number of people occupying the room and the number of lights.
If the AC is on for 9 hours a day, the power consumption per day will be 1.32x9=11.88 or say 12 units per day. So in a month a 1 ton AC working 9 hours every day will consume 12x30=360 units of electricity.