DC magnetic circuit

[CHRIS_18]

Hey guys I have trouble solving this problem so any help will be appreciated! The problem is C1 in the picture.

 

[Alec_t]

Since this is Homework Help, not "Homework Done for You", please post your best effort so far at a solution based on your class-work.

 

[CHRIS_18]

Well, I think to find the total Reluctance and the lengh.It will be a good start and after that use the magnetic reluctance formula.

 

[Arouse1973]

There are two other thing you need to factor in. One is related to a vacuum and the other has a measurement of distance (you mentioned this above). See if you can find the missing two.
Thanks
Adam