A group of friends are going on a day out to Project Hilsha. They divided their route into 3 equal parts, and planned on maintaining an average speed of 68 km/h on their way to their destination....

A group of friends are going on a day out to Project Hilsha. They divided their route into 3
equal parts, and planned on maintaining an average speed of 68 km/h on their way to their
destination. Their speed for the first and second part were 72 km/h and 88 km/h respectively.
What speed should they maintain for the third part of their journey if they are to achieve their
target average speed?