Question about analyzing forces

[jaja1990]

In a try to test my knowledge of Newton's laws, I have posed the following question to myself.

Object A | Object B | Object C

Object A pushes on B by an amount of 60N

Object B pushes on A by an amount of 30N

Object C pushes on B by an amount of 10N

What is the resultant force of each object?

My attempt:

(The arrows indicate direction.)

Considering A and B:
A pushes on B by 60, so F_AonB = 60→
B reacts on A by 60, so F_BonA = 60←
B pushes on A by 30, so F_BonA becomes 90←
A reacts on B by 30, so F_AonB becomes 90→

Considering B and C:
C pushes on B by 10, so F_ConB = 10←
B reacts on C by 10, so F_BonC = 10→

Considering A and B (after considering C on B):
B pushes on A by 100, so F_BonA = 100←
A reacts on B by 100, so F_AonB = 100→

Conclusion:
A pushes 100→
B pushes 100← and 10→
C pushes 10←

I have been informed that the solution is invalid, and that the question itself is wrong. Can you tell me why the problem is wrong/invalid?
Someone tried to explain to me, but I didn't really understand.

 

[Doc Al]

I have been informed that the solution is invalid, and that the question itself is wrong. Can you tell me why the problem is wrong/invalid?

For one thing:

Object A pushes on B by an amount of 60N

Object B pushes on A by an amount of 30N

This contradicts Newton's 3rd law.

A and B will exert equal and opposite forces on each other.

 

[jaja1990]

Thanks for the simple answer.