A Conducting Bar Moves as Shown near a Long Wire

A conducting bar moves as shown near a long wire carrying a constant 80-A current. If a = 1.0 mm, b = 20 mm, and v = 5.0 m/s, what is the potential difference, V_a − V_b?

A) −0.24 mV
B) +0.24 mV
C) −0.19 mV
D) +0.19 mV
E) −0.76 mV