Update 2
Updated: BL combined with del(N_co2) and K_abs.

Fixed all problems. This is the final version of the code which uses the
entire Fw eqn (del rho AND rel perms)
Update 2
Update 2: fixed BL FINAL form, uses del(rho) and rel perms in Fw

Tr = [ del (N_co2) + v_BL +k_avg ]