Two Velocities in a Traveling Wave

[Solis]

Homework Statement

http://img258.imageshack.us/my.php?image=mphw0xj.png

The answer I tried is selected.
Edit: Nevermind, I figured out that v_x = 0. The string doesn't move in the x direction while the wave does. (v_p is the velocity of the wave)

 

[berkeman]

Glad you figured it out. I moved this from Advanced Physics to Intro Physics, BTW.