Three:
One to write the light bulb removal program,
one to write the light bulb insertion program, and
one to act as a light bulb administrator to make sure nobody else tries to change the light bulb at the same time.
  
               
   
            
            
			
       
           
       
           
            or
           
       
      
       
            
             
			 
			2 years old.
Cow: "Mooooove over"
Sheep: "Naaaaaaa."
  
               
   
            
            
			
       
           
       
           
            or
           
       
      
       
            
             
			 
			"Ten billion dollars and high cholesterol!" 
  
               
   
            
            
			
       
           
       
           
            or