31857
In particle physics , a system of " natural units " in which the speed of light in vacuum " c " and the reduced Planck constant " ħ " are dimensionless and equal to unity is widely used : .
 person: Planck
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: Planck 
Answer:
 person: Planck