45713
The 1912 discovery of the amplifying ability of the Audion vacuum tube , invented in 1906 by Lee de Forest , solved these problems .
 person: Lee de Forest
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: Lee de Forest 
Answer:
 person: Lee de Forest