End to end delay with MM1 queue
Hint:
         _______
TX  ____|message|_______________________
                          _______
RX  _____________________|message|______
        &lt;----------------&gt;           (a)
     or &lt;------------------------&gt;   (b)

Where does the delay end? At (a) or (b).
Update your question with your thoughts and calculations for the rest of the question.