Sound waves propagate through a media as pressure waves that cause the media to go through isentropic

Question:

Sound waves propagate through a media as pressure waves that cause the media to go through isentropic compression and expansion processes. The speed of sound c is defined by c2  (P/) s and it can be related to the adiabatic compressibility, which for liquid ethanol at 70 F is 6.4 in 2/lbf. Find the speed of sound at this temperature.