The normal force on the bottom crate is 539 N.
The normal force on the middle crate is 294 N.
The normal force on the top crate is 98 N.
How to calculate the normal force on each crate?
The normal force on an object is the upward force exerted on an object by the surface on which the object rest on.
The normal force on each crate is calculated by applying the following formula as shown below.
The normal force on the bottom crate:
Fn = mg
Fn = (25 kg + 20 kg + 10 kg) x 9.8 m/s²
Fn = 539 N
The normal force on the middle crate:
Fn = (20 kg + 10 kg) x 9.8 m/s²
Fn = 294 N
The normal force on the top crate:
Fn = (10 kg) x 9.8 m/s²
Fn = 98 N