How do you calculate relative permeability in a loud speaker?

[copresh1]

i am a bit confused as to where to start on this problem, any hint will be appreciated.(problem attached)

 

[berkeman]

What is the equation for the force on a current-carrying wire in a magnetic field? What is the equation for the magnetic field generated by an air core coil? How can you use these two equations to help you solve this problem?

 

[copresh1]

F=BLI
where B is flux density,L is length of conductor, and I is the current in the conductor.
magnetic field density=magnetic flux/c/s area
magnetic flux=mmf/reluctance
& reluctance=lenght of airgap/mew0 * c/s A

 

[copresh1]

using f=BLI i found B=100T
next i used S=L/mew0*crosssectional area of air gap(L=10mm,c/sarea airgap=piD=3.14*0.001)
=2533029.59A/wb
next using H=IN/L(I=100mA,N=50,L=15mm this assumed)
=333.33A/m
but when i go to find relative permeabilty i am getting a huge value which i think is wrong.
apart from that my understanding is that i there are three elements involved here ie the coil,the magnet,the airgap(am i right?)but how do i find the mmf of the magnet bcoz i cannot find the reluctance of the magnet

 

[berkeman]

How huge is the $$\mu_0$$ value that you are getting? The relative permeability of magnetic materials can be quite high, in the tens of thousands for some materials.

 

[copresh1]

sorry for the delay in responding
the value i get for relative permeability is 238734.802
i will scan and attach the method that i have followed to solve the prob till now.