Answer:
b. 375 N
Explanation:
System of forces in balance
ΣFy = 0 Equation (1)
Forces acting on the board
Tâ: Tension in the  left chain ,  vertical and upward
Tâ = 250 N : Tension in the right chain , Â vertical and upward
Wâ = 125 N : Weight of the  board , vertical and downward
Wâ =  500 N : Weight of the  person , vertical and downward
Calculation of the Tâ
We apply the Equation (1)
ΣFy = 0 Â
Tâ+Tâ-Wâ-Wâ = 0
Tâ = -Tâ+Wâ+Wâ
Tâ = -250 N+ 125 N+ 500 N
Tâ = 375 N