Certain doctors determine blood pressure with a mercury manometer. While the heart is beating, blood pressure changes by $5.6\,\text{kPa}$. The density of mercury is $14\,000\,\text{kg m}^{-3}$ and the gravitational field strength $g$ is $10\,\text{N kg}^{-1}$. What is the corresponding change in the height difference between the levels in the manometer during a heartbeat?
- A$40\,\text{mm}$
- B$80\,\text{mm}$
- C$400\,\text{mm}$
- D$800\,\text{mm}$