BOTH INTERNATIONAL & INLAND What is the minimum vessel length which must show two white masthead lights, one forward and one aft, when underway at night?

Under Inland Navigation Rules, for the condition where 'What is the minimum vessel length which must show two white masthead lights, one forward and one aft, when underway at night', the correct requirement is: '50 meters'. This standard ensures clear navigational intent and collision avoidance.