Question 5

The distance between Town Y and Town Z is 7 km .
At the beginning , both Ali and Bob are at Town Y .
Ali walked from Town Y to Town Z at a constant speed .
After Ali had walked for 1 km , Bob discovered that Ali had left his belongs at Town Y .
Bob immediately ran after Ali at a constant speed of 4 km/h .
After handing over the belongings to Ali , Bob turned back and started running towards Town Y at the same speed .
Given that both Ali and Bob reached Town Z and Y respectively at the same time , what was Ali's speed ?