physics
posted by physics im dying .
An insulated copper wire is wrapped around an iron nail. The resulting coil of wire consists of 240 turns of wire that cover 1.8 cm of the nail, as shown in the figure . A current of 0.61 A passes through the wire.
if the ferromagnetic properties of the nail increase the field by a factor of 120, what is the magnetic field strength inside the nail?
Express answer in T
iv been trying for soo long but i have no idea , its a hmk question can someone explain to me , i have a test tomm

B= 120*N*I*4PI*10^{7}/(2*radius)

so n = 240 and i is 0,61??
and would the radius be 0.018/2?? 
B=u0*I*N/L
u0=4pi*10^7
I= .61A
N=240
L=.018m
B=.0102T
Multiply B times an increase of 120
Answer=1.2T