Explanation:to find the area you must first find the radius given you have the diameter you cut the diameter in half giving you 40 then you follow the formula “A= (pie)r (squared) leaving you with 
answer:5024
        
             
        
        
        
I believe you're talking about displacement. It's a directional vector that depicts the movement of a point between two instances.
 
        
             
        
        
        
It looks blue as it is only reflecting blue light
        
             
        
        
        
law of conservation of energy 
aka the first law of thermodynamics