Formula:
F = ma
F: force (N) m: mass (kg) a: acceleration (m/s^2)
Solution:
F = ma
F = 20 × 10
 = 200N
        
             
        
        
        
It might be c I'm not sure either. Hope I helped
        
             
        
        
        
If he is jumping you are adding force which means that you will be falling twice as fast
        
             
        
        
        
Answer:
 1800J
Explanation:
Given parameters: 
Weight of the book  = 20N 
Total distance covered  = 45m + 15m + 30m  = 90m 
Unknown: 
Total work performed on the books  = ? 
Solution: 
To solve this problem we must understand that work done is the force applied to move a body through a certain distance. 
 So; 
     Work done  = Force x distance 
   Work done  = 20 x 90  = 1800J