Purity of Mohr's salt

You will finish a calculation of the percentage purity of a sample of Mohr's salt from a permanganate titration. The sample of 1.960 g was made up to 100.0 mL. A portion of 10.0 mL was titrated with permanganate of concentration $0.0200\ \text{mol/L}$.

The idea. One permanganate ion takes five iron(II) ions. Each formula unit of Mohr's salt, $392\ \text{g/mol}$, holds one iron(II) ion.

Your tasks.

1. Complete moles_permanganate(c, titre_ml). It returns the amount of permanganate in moles.
2. Complete moles_iron(n_mno4). It returns the amount of iron(II) that reacts with that permanganate.
3. Complete purity(sample_g, flask_ml, aliquot_ml, n_iron_aliquot). It scales the iron(II) up to the whole flask, finds the mass of pure Mohr's salt, and returns the percentage purity.