275 square feet
Yes, a 4.5 ton air conditioner would be the minimum size for 2000 square feet.
A 15000 BTU air conditioner can cool an area of up to 750 square feet. Larger areas can be cooled but will be ineffective and put a strain on the unit.
24000 sq ft = 2229.67 sq metres (to 2 dp)
24000 square feet.
A 13000 BTU air conditioner will cool an area of around 550 square feet. The BTU rating determines how much heat can be removed from the are over a given amount of time.