In Book 2, Lesson 13, you learned how to play the C position and the F position with your right hand. In some songs you must play the C and F positions with your left hand.
In this song, both the left and right hands move between the C position and the F position. The left hand plays the melody and the right hand plays the accompaniment. In the final bar, both hands play the melody.
Here is a new version of the previous song. Once again both the left and right hands move between the C position and the F position. This time the right hand plays the melody and the left hand plays the accompaniment.