A Long Solenoid with 15 Turns Per Centimeter Has a Core

Multiple Choice

A long solenoid with 15 turns per centimeter has a core of annealed iron.When the current is 1.00 A,the magnetic field inside the iron core is 2.46 T.The applied field _app is approximately

A) 18.8 $\mu$ T
B) 2.46 T
C) 4.32 mT
D) 3.87 T
E) 1.88 mT