Answer :
In order to find the value of N in the equation when T = 60, we just need to apply the value of T and then calculate the value of N.
So we have that:
[tex]\begin{gathered} T=50+\frac{N-40}{4} \\ 60=50+\frac{N-40}{4} \\ \frac{N-40}{4}=10 \\ N-40=40 \\ N=80 \end{gathered}[/tex]So the number of chirps per minute is 80