An infinitely long straight conductor and a flat rectangular contour with sides a and b and with N turns lie in a single plane. The distance between the straight conductor and the side of the contour closest to the straight conductor is c. Determine the following quantities: (1) the mutual inductance of the conductor and the contour, (2) the quantity of electricity induced in the contour if the contour is rotated through `90^@` about the AB axis provided that a current I is flowing in the contour and the resistance of the contour is R, (3) the work that must be done to rotate the contour through 1800 about the AB axis provided that there is current I both in the long conductor and in the contour and that the sense of the current in the contour is clockwise (in the plane of the drawing).