Two calorimeters A and B contain equal amounts of water at temperatures ${48}^{0}C$  and  ${80}^{0}C$  respectively. Mass of water in each of the calorimeters is 300g. From calorimeter A, 100g water is transferred into B and stirred until thermal equilibrium is established, then 100g water is transferred from B to A and stirred until thermal equilibrium is established. How many times this cycle has to be repeated until, the difference between the temperatures of the calorimeters becomes less than or equal to ${1.0}^{0}C$ . Neglect water equivalent of the calorimeters, work done in transferring the liquid, work done in the stirring and heat loss to the surroundings.