<span>They are balanced. If the forces were not balanced the book would move*. In this example, the downward force of gravity on the book is counterbalanced by the upthrust of the desk. </span>
Explanation:
In the parallel combination, the equivalent resistance is given by :

4. When three 150 ohms resistors are connected in parallel, the equivalent is given by :

5. Three resistors of 20 ohms, 40 ohms and 100 ohms are connected in parallel, So,

Hence, this is the required solution.
Answer:
I'm pretty sure it's all of them i'm not completely sure though hope it helps anyways! :)