A coordinate plane with Number of Text Messages on the x-axis and Number of Minutes Used on the y-axis, with points plotted at, (10, 20), (20, 40), (30, 60), and (40, 80). A prepaid cell phone charges a preset number of minutes to use text messaging. The graph represents y, the number of minutes used for x, the number of text messages sent and received. Is there a direct variation? Which equation represents the relationship?

Yes, y = 2x.
Yes, y = 20x.
No, y = x + 10.
No, y = x + 20.