Average Speed of Ali's trip

An easy puzzle to start your day with:

There was a salesman named, Ali. Who had to drive to city B to sell his products. Ali is currently at location A. He can drive at different speeds throughout the journey.

For, the first half of the distance of his journey, he decided to travel it with an average speed of 80 km/h. (km/h means kilometres per hour). In this half of the journey, he doesn't change his speed in between. Rather, the speed stays the same throughout the first half, which is equal to 80 km/h.

After, finishing the first half of the journey, he travels the next half of the trip with a constant speed of 120 km/h. Now, we have to find, the average speed of Ali, for the whole journey?

Now, if we also include the return journey from City B to City A. Where, Ali travels at the speed of 80 km/h throughout the journey. What can be said about his round trip average speed? Can we know exact round trip average speed of Ali or we need the distance parameter specified in the question to find the average speed?

All the discussion of this puzzle, I leave it to your brain. Make cells of your brain fight for the answer. I have faith in you all LLs. You will surely get to the answer. See you all. All the best to solve the puzzle. I will be there, after sometime with another interesting puzzle. Till then, good bye.

An Easy One:
A salesman drives from A to B. The first half of the distance of his journey, he drives at constant speed of 80 km/h and the second half of his journey, he drives at a constant speed of 120 km/h. What is the salesman's average speed for the complete journey?