Lenz's Law: in the Figure, a Straight Wire Carries a Steady

Lenz's law: In the figure, a straight wire carries a steady current I perpendicular to the plane of the page. A bar is in contact with a pair of circular rails, and rotates about the straight wire. The direction of the induced current through the resistor R is

A) from a to b.
B) from b to a.
C) There is no induced current through the resistor.