Answer:
The value is

Step-by-step explanation:
From the question we are told that
The acceleration is

Generally the force by which the truck bed (truck) is moving with is mathematically represented as

Now for the truck cabinet to slip from the truck bed then the frictional force between the truck cabinet is equal the force by which the the truck bed is moving with that is

Here
is the frictional force which is mathematically represented as

substituting into above equation

=>

substituting values

