A very long, straight solenoid with a cross-sectional area of 6.15cm squared is wound with 50 turns of wire per centimeter, and the windings carry a current of 0.235A . A secondary winding of 2 turns encircles the solenoid at its center. When the primary circuit is opened, the magnetic field of the solenoid becomes zero in 4.80×10?2s. What is the average induced emf in the secondary coil?