Ha figure is a sectional area of a long coaxial cable. The radius of its metal strands are R1 = 3 mm, R2 = 4mm, r = 2mm, and the currents in them I1 = 15A, I2 = 10 A. Considering that the currents flow in the same direction, to construct a graph of the scale of the magnetic induction field of the distance from the cable axis in = B (r). Determine the magnetic energy stored between the metal conductors of the cable per unit length.