A Rod with Resistance R Lies Across Frictionless Conducting Rails

Multiple Choice

A rod with resistance R lies across frictionless conducting rails in a constant uniform magnetic field B, as shown. Assume the rails have negligible resistance. The magnitude of the force that must be applied by a person to pull the rod to the right at constant speed v is:

A) 0
B) BLv
C) BLv/R
D) B²L²v/R
E) B²Lxv/R