A manometer filled with water is used to find the pressure of a gas supply, as illustrated. The density of water is $1000\,\text{kg m}^{-3}$. What is the pressure of the gas supply?
- A$300\,\text{Pa}$ above atmospheric pressure
- B$400\,\text{Pa}$ above atmospheric pressure
- C$3000\,\text{Pa}$ above atmospheric pressure
- D$4000\,\text{Pa}$ above atmospheric pressure