What is the effective nuclear charge of iron for 3d and 4s electron?

The atomic number of Fe is 26, and thus the nuclear charge of Fe is 26.
The electron configuration of Fe : 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²

3d orbital is in the 3rd shell, and thus the inner shells including the 1st and 2nd shells (1s² 2s² 2p⁶).
Number of electrons in the inner shells = 2 + 2 + 6 = 10
Effective charge of Fe for 3d electron = 26 - 10 = 16

4s orbital is in the 4th shell, and thus the inner shells including the 1st, 2nd and 3rd shells (1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶).
Number of electrons in the inner shells = 2 + 2 + 6 + 2 + 6 + 6 = 24
Effective charge of Fe for 4s electron = 26 - 24 = 2