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Design a machine of the following language: 

 

L = Exactly two a’s where ∑ = {a, b}

 

Answer:

 

Strings of the given language,

L = Exactly two a’s is L = {aa, aab, aba, baba, bbaa, ……}. 

 

We know what the procedure to design a machine is first we design a machine for the minimum string ‘aa’.

 

RE = b*ab*ab*