Mechanics

The rod is now fixed horizontally. The ring is in equilibrium with the string taut and in a vertical plane, and making an angle of 45 degrees below the horizontal. The tension in the string is equal to TN. Given that the equilibrium is limiting, find the value of T correct to 3 significant figures.

I've been stuck on this question for a very long time, and I am unclear as to how I could possibly solve it as there are too many unknowns.
Here is the full link to the question: https://isaacphysics.org/questions/ft_upper_q7b_stage2_mech_2018?board=maths_mech_s2_t7&stage=a_level
Part D