In {HEAD ~ an exemplary embodiment} of {TAIL ~ the present invention}, the step of displaying the volume control menu window on the display unit converts the volume control menu window on the display unit to a volume control menu window for the speakers when the external audio reproduction unit is released from the audio output port 
In { HEAD ~ an exemplary embodiment } of { TAIL ~ the present invention } , the step of displaying the volume control menu window on the display unit converts the volume control menu window on the display unit to a volume control menu window for the speakers when the external audio reproduction unit is released from the audio output port
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