VTMO 2021 — Grade 3 — titan-cup Question 11

An travels $S$ → A $_{1}$ → A $_{2}$ → $F$ and Binh $S$ → $B _{1}$ → $B _{2}$ → $F$. An’s route is $10 m$ longer. How much longer is A $_{2} F$ than $B _{2} F$?