Use Saha-Boltzmann statistics to get the relative number densities

[Zapped17]

Homework Statement

Use Saha-Boltzmann statistics to get an idea of the relative number densities of H, H+, H−, and H(n = 3).
Gather information from Gray’s book concerning the partition functions (hint: with its two electrons H−
is He-like; H+ is a naked proton, so U(p) = 1), the electron pressure, and so on. Assume T = 5772 K
(S 0 = 1, as Gray labels it in the relevant plots) and solar surface gravity. Take care with the units!
· What do you learn from comparing N(H−) and N(H, n = 3)?

Relevant Equations

The Saha equation N_i+1/N_i
for i:s energy levels.

When I am using the Saha equation, how i am suppose to know the electron pressure?
Which are required to calculate the ration?
Since: P_e = n_ekT (electron pressure and n_e is related to each other, but n_e is also unknown based on my understanding).