The Variation in the Pressure of Helium Gas,measured from Its $\Delta$

Multiple Choice

The variation in the pressure of helium gas,measured from its equilibrium value,is given by $\Delta$ P = 2.9 *10 ^{- 5} cos (6.20x - 3 000t) where x and t have units m and s.Determine the speed (in m/s) of the wave.

A) 1 515
B) 153
C) 484
D) 828
E) 101