37720
Like most of Blackburn 's aircraft of the time , the fuselage was built up around four steel longeron s ; it was duralumin covered from nose to just aft of the rear observer/gunner 's cockpit , the rest fabric covered .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities:  
Answer:
 None