Step: 1

Given
Coefficient of static friction, 
Coefficient of kinetic friction, 

Step: 2

Let us draw the free-body diagram of the system.

Step: 3

a)
First apply the equilibrium condition,



Now, 


Apply the equilibrium condition,

Step: 4

Let us draw the free-body diagram of the second block.

Step: 5

Apply the equilibrium condition,


Now, 

Step: 6

Apply the equilibrium condition, 


Therefore, the force is 

Step: 7

b)
Without the cable, both blocks will stay together and motion will impend only at the floor.
Now, apply the equilibrium condition, 


Now, 

Step: 8

Apply the equilibrium condition, 


Therefore, the force is 

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