1. **State the problem:** We are given two points on a linear function representing temperature $y$ in degrees Fahrenheit based on the number of cricket chirps $x$. The points are $(40, 50)$ and $(80, 60)$. 2. **Formula for rate of change (slope):** The rate of change of a linear function is the slope $m$ calculated by $$m = \frac{y_2 - y_1}{x_2 - x_1}$$ where $(x_1, y_1)$ and $(x_2, y_2)$ are two points on the line. 3. **Apply the formula:** Using the points $(40, 50)$ and $(80, 60)$, $$m = \frac{60 - 50}{80 - 40} = \frac{10}{40}$$ 4. **Simplify the fraction:** $$m = \frac{\cancel{10}}{\cancel{40}} = \frac{1}{4}$$ 5. **Interpretation:** The temperature increases by $\frac{1}{4}$ degree Fahrenheit for each additional cricket chirp per minute. **Final answer:** The rate of change is $\frac{1}{4}$ degree Fahrenheit per chirp.