Answer
Wire B exerts more force on the block.
Work Step by Step
We can consider the torque with respect to a rotation axis at the block's center of mass.
There is a clockwise torque due to wire A and a counterclockwise torque due to wire B. Since the system is in equilibrium, the magnitudes of these two torques are equal.
The magnitude of the torque due to wire A is equal to the magnitude of the torque due to wire B.
Note that: $~~\tau = r_\perp F$
Since the horizontal distance from the block's center of mass to wire B is less than the horizontal distance from the block's center of mass to wire A, then wire B exerts more force on the block.
