Mountain bike wheels are usually assembled using thin metal rods (spokes) that attach the wheel rim to the central hub. To keep the wheel rim "true" (i. e.perfectly round), one tries to keep all the spokes under the same tension. One way to determine tension is to quickly and gently strike the spoke somewhere along its length, causing it to vibrate transversely. The sound given off by the vibrating spoke indicates its tension. Assume a spoke has length L, linear mass density p, and is under tension T. The spokes are rigidly clamped at both ends and do not mutually interact (i. e. no spokes touch each other). Assume the vibrating spoke is like a vibrating string. The velocity of sound in air is vs. What four lowest frequencies might be "excited" by the mechanical strike?