As shown in the figure, a straight conductor parallel to thex-axis can slide without friction on top of two horizontal conducting rails that are parallel to they-axis and a distance ofL=0.4m apart, in a vertical magnetic field of 1 T. A58-A current is maintained through the conductor. If a string is connected exactly at the center of the conductor and passes over a frictionless pulley, what massmsuspended from the string allows the conductor to be at rest?