Correct answer: 6 √2
The time period of a satellite is proportional to the square root of the cube of its orbital radius (Kepler's Third Law). For the second satellite at a height of 2R, the orbital radius is 3R. Comparing with the geostationary satellite (orbital radius 6R, time period 24 hours), the time period is T = 24 × (3/6)^(3/2) = 6√2 hours.