<span>Newton's Third Law of Action-Reaction is that for each and every action that happens, there is an equal and opposite reaction to it. In the scenario of a roller coaster, this is when you push down on the seat of the roller coaster as it flies along and the seat pushes back against you.</span>
The tension in the string with friction would be the biggest because of the involvement of the force of gravity. This would result in that the friction force that is acting on the system. There is no friction in the frictionless system, and only the force of gravity is relevant.
