Answer
$$T=466 \mathrm{\ N}$$
Work Step by Step
the total upward force on chair and man is $ 2T$.
Thus, by using Newton's second law which leads us to
$$
(2 \times T)-(m \times g)=(m \times a)
$$
so that when $a=0,$ the tension is $T=466 \mathrm{\ N}$
