Answer:

Step-by-step explanation:
The attached figure shows the whole description. Considering the applied force is 100 N.
The acceleration of both blocks A and B,

Firstly calculating the mass m using the second law of motion as :
F = ma
m is the mass


m = 125 kg
It suddenly encounters a surface that supplies 25.0 N a friction, F' = 25 N



So, the new acceleration of the block is
. Hence, this is the required solution.