A conducting bar rests on two parallel horizontal rails 50 cm apart forming a square area. The resistance of the bar and the rails is assumed to be constant and equal to 0.05 ??. A uniform magnetic field 0.5 T is perpendicular to the plane of the rails. The value of the field is uniformly reduced to zero in a time of 0.1 s. What is the maximum value of the force acting on the bar during that time?