1. **State the problem:** We need to find the interval over which the function $m$ is negative. 2. **Analyze the function:** The function $m$ is a decreasing straight line that crosses the y-axis at 4 and the x-axis at 6. 3. **Key points:** - The y-intercept is at $(0,4)$. - The x-intercept is at $(6,0)$. 4. **Determine where $m$ is negative:** - Since the line crosses the x-axis at $x=6$, the function value changes sign there. - For $x < 6$, the function is above the x-axis (positive). - For $x > 6$, the function is below the x-axis (negative). 5. **Conclusion:** The function $m$ is negative on the interval $(6, \infty)$. **Final answer:** B. $(6, \infty)$