This has been discussed before.

Directly from NWA's US website...

Elite Qualifying Fare Classes
Elite Qualifying Miles at 150%: P, F, J, C, Z, Y, B
Elite Qualifying Miles at 100%: M, H, Q, V, L, T, K
Elite Qualifying Segments: P, F, J, C, Z, Y, B

B class will earn 50% extra EQM here in N.A.

-RM