If ƒ={(5, , , , , 7)}, then the range of ƒ is

1. The points are in given in the form (x, y) : (x-coordinate, y-coordinate).
2. The range is the set of values onto which ƒ sends the x's.

The x's are sent onto the values 1, 2, 3, 1, 7 -> {1,2, 3, 7} (after removing duplicates)