Using the lattice constant of iron r = 2.87 , and assuming the spins are parallel and aligned along the same axis, estimate J for

Using the lattice constant of iron r = 2.87 Å, and assuming the spins are parallel and aligned along the same axis, estimate J for the interaction (10.8.1). Then estimate the interaction J for iron using T_c = 2Jz/kB as defined in Section 10.3, assuming z = 8 for a bcc crystal, and knowing the Curie point of iron of 770° C = 1043 K. How do the two values compare?

Hint 2 4 4r3 (1) (zW.(2 3W.)(2).n)), (10.8.1)