The answer given is NO.
I have a doubt. When concatenating two languages, we take the strings of the first language and concatenate it with each string of the second language. So if I go by the definition only, the above statement is correct.
But by taking a few examples, it seems that when we concatenate two languages, some of the strings comes out to be the same. The final concatenated language will contain strings less than |L1| * |L2|.
Therefore, the correct relation should have been |L1. L2| <= |L1| x |L2|.
Is this the right logic to answer this question? Or did I miss out on any conceptual reasons?