Answer:
Displacement is zero.
Average velocity 7,2 km/hr
Step-by-step explanation:
In order to calculate the average velocity we just ahve to do a simple rule of three, where 20 minutes is divided by 2,4 kilometers, so how much would she advance in 60 minutes?:

So her average veocity will be 7.2 km/hr
And her displacement will be zero because she was on a treadmill so her location didn´t change at all.