Chapter 1 - Introduction to Physics - Problems and Conceptual Exercises - Page 17: 56

C

$N=T-40.0$ For $T =65.0,~N=65.0-40.0=25.0~chirps/13~s$ $1~s=9,192,631,770~cycles=9.19263177\times10^{9}~cycles$. See page 4. $1~chirp=(1~chirp)(\frac{13~s}{25.0~chirps})(\frac{9.19263177\times10^{9}}{1~s})=4.78\times10^{9}~cycles$