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 relative permeability K_m is approximately

A) 1800
B) 1310
C) 7.64 $\times$ 10^-4
D) 5.56 $\times$ 10^-4
E) 1500