long solenoid has a diameter of 12.0 cm.when a current i exists in its windings, a uniform magnetic field of magnitude b 30.0 mt is produced in its interior. by decreasing i, the field is caused to decrease at the rate of 6.50 mt/s. calculate the magnitude of the induced electric field (a) 2.20 cm and (b) 8.20 cm from the axis of the solenoid.