Reading a chromatogram

A food colour is run on paper next to three known dyes. The solvent rises $11.2\ \text{cm}$, and the colour gives two spots, at $2.0\ \text{cm}$ and $6.9\ \text{cm}$. You will make the program find the $R_f$ of each spot, name each dye from a table, and predict how far one dye would rise if the solvent went $15\ \text{cm}$.

The idea. $R_f = \dfrac{\text{distance of the spot}}{\text{distance of the solvent}}$. In the same solvent, a dye always has the same $R_f$.

Your tasks.

1. Inside the first loop, work out rf for each spot.
2. Inside the second loop, keep the name of the known dye whose $R_f$ is closest: set best and gap when diff is smaller than gap.
3. Find far, how far sunset yellow would rise if the solvent rose $15\ \text{cm}$.