A graph shows a plant's height in cm on the vertical axis against the week number on the horizontal axis. The plotted points are (1, 4), (2, 7), (3, 11) and (4, 11). Between which two weeks did the height stay the same?

Two perpendicular axes — horizontal $(x$-axis) and vertical $(y$-axis) — meet at the **origin** (0, 0). Together they divide the plane into four **quadrants**:

- **I**: $x>0,y$ > 0 (top right)
- **II**: $x<0,y$ > 0 (top left)
- **III**: $x<0,y$ < 0 (bottom left)
- **IV**: $x>0,y$ < 0 (bottom right)

Points ON the axes don't belong to any quadrant. (a, 0) sits on the $x$-axis; (0, b) sits on the $y$-axis.