Answer:
a) N = 343 [N]
Explanation:
We must remember Newton's third law, which tells us that the force acting on a body is equal to the normal reaction force of equal magnitude but acting in the opposite direction.

where:
m = mass = 35 [kg]
g = gravity acceleration = 9.81 [m/s²]
![N = 35*9.8\\N= 343 [N]](https://tex.z-dn.net/?f=N%20%3D%2035%2A9.8%5C%5CN%3D%20343%20%5BN%5D)
Answer is d using a heavier string
The answer to that probably would be C excuse me if I am wrong.