Answer: 
Explanation:
Given
Intensity must be reduced by a factor of 6
Intensity is given by 
Substitute
by 

So, the disk must be rotated by an angle of
.
Here the block has two work done on it
1. Work done by gravity
2. Work done by friction force
So here it start from height "h" and then again raise to height hA after compressing the spring
So work done by the gravity is given as

Now work done by the friction force is to be calculated by finding total path length because friction force is a non conservative force and its work depends on total path


Total work done on it

So answer will be
None of these
Force is equal to mass multiplied by acceleration, therefore
F=ma
m=2569.6 kg
a=4.65m/s^2
therefore F=2569.6*4.65=11948.6 (correct to 1 d.p.)