r₁+r₂.........6 ore..........1 bazin
r₂.............10 ore..........1 bazin ⇒r₂.............30 ore..........3 bazine
r₁+r₂.........6 ore..........1 bazin ⇒r₁+r₂.........30 ore..........5 bazine ⇒
5-3=2bazine
r₁..............30 ore..........2 bazine ⇒ r₁ va umple 1 bazin in 30:2=15 ore