A circular coil has a 12.8cm radius and consists of 29.0 closely wound turns of wire. An externally produced magnetic field of magnitude 2.23 mT is perpendicular to the coil. (a) if no current is in the coil, what magnetic flux links its turn? (b) When the current in the coil is 5.47A in a certain direction, the net flux through the coil is found to vanish. What is in henrys the inductance of the coil?