Please show me how to get the R_f value of each spot for both Figure 1 and 2 by using the centre of each spot.

Pyridine, Benzaldehyde, Unknown E / Pyridine, Benzaldhyde, Inconnu E Part A/ Partie A Solvent system / Systme de Solvant 1:3 EtoAc/Hexane Legend / Lgende Pyr. = Pyridine Co = Co-Spot E = Unknown E / Inconnu E By CO E Figure 1 - Pyridine & unknown E / Pyridine et Inconnu E Solvent system / Systme de Solvant 1:3 EtoAc/Hexane Legend / Lgende Benzal. = Benzaldehyde / Benzaldhyde Co = Co-Spot E = Unknown E / Inconnu E Sareil Figure 2 - Benzaldehyde & Unknown E/ Benzaldhyde et Inconnu E