What is the magnitude of the magnetic field? - EM Field and Photons

A conducting bar slides without friction on two parallel horizontal rails that are 64 cm apart and connected by a wire at one end. The resistance of the bar and the rails is constant and equal to 0.08 Ω. A uniform magnetic field is perpendicular to the plane of the rails. A 0.08-N force parallel to the rails is required to keep the bar moving at a constant speed of 0.4 m/s. What is the magnitude of the magnetic field?  Answer in Tesla, with two decimal places.