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Let Σ = {a, b}. For a word w ∈ Σ* , let na(x) denote the number of a’s in w and let nb(x) denote the number of b’s in w. Consider the following language: 
L := {xy | x, y ∈ Σ* , na(x) = nb(y)} 
What can we say about L?

   
   
 

(A) L is regular, but not context-free.

 

(B) L is context-free, but not regular.

 

(C) L is Σ*.

 

(D) None of these.

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