Incorrect Answer.

C{1,2} K1p K2p, is valid in KT45n, but K1p K2p C{1,2}p is not, ie. agents 1 and 2 both knowing p does NOT make it common knowledge among the two of them. In the following KT45n model, world x satisfies K1p K2p. If it also satisfied C{1,2}p then K1 K2p would also be true at world x, but K1 K2p is clearly false at x.


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