The problem statement states that block B moves towards the right with an acceleration of 'b'. We need to find the net acceleration of block A. To solve this problem, let's break it down into smaller steps:

1. Understanding the scenario:
- There are two blocks, A and B.
- Block B is moving towards the right with an acceleration of 'b'.
- The net acceleration of block A needs to be determined.

2. The forces acting on block A:
- Normal force (N): The force exerted by the surface on block A perpendicular to the surface.
- Frictional force (f): The force exerted by the surface on block A parallel to the surface.
- Gravitational force (mg): The force exerted on block A due to gravity.

3. Analyzing the forces:
- Since block B is moving towards the right with an acceleration of 'b', there must be a force acting on it. This force is exerted by block A on block B and is equal to the product of the mass of block B and its acceleration, which is 'mb * b'.
- According to Newton's third law of motion, there is an equal and opposite force acting on block A by block B, which is '-mb * b'.

4. Applying Newton's second law of motion:
- The net force acting on block A is the sum of the forces acting on it. This can be expressed as:
Net force = ma (mass of block A) * aa (acceleration of block A)

- The forces acting on block A are:
Net force = -mb * b (force exerted by block B on block A) + f (frictional force) + mg (gravitational force) + N (normal force)

5. Determining the net acceleration of block A:
- Since the net force acting on block A is equal to the mass of block A times its acceleration, we can equate the two expressions:
ma * aa = -mb * b + f + mg + N

- Rearranging the equation to solve for the net acceleration 'aa':
aa = (-mb * b + f + mg + N) / ma

6. Solving for the net acceleration:
- To find the value of the frictional force, we need to use the equation: f = μN, where μ is the coefficient of friction between block A and the surface.
- The normal force N can be calculated as: N = ma * g, where g is the acceleration due to gravity.

- Substituting the values into the equation for net acceleration:
aa = (-mb * b + μ * ma * g + ma * g + ma * g) / ma
aa = (-mb * b + (2 + μ) * ma * g) / ma

- Simplifying the equation:
aa = -mb * b / ma + (2 + μ) * g

Therefore, the net acceleration of block A is given by the expression: aa = -mb * b / ma + (2 + μ) * g.

Question incomplete