A fixed mass of gas is enclosed in a sealed syringe at a pressure of $100\,\text{kPa}$. The plunger is then pushed in slowly until the pressure becomes $80\,\text{kPa}$. At that point, the gas has a volume of $50\,\text{cm}^3$. The temperature of the gas remains unchanged. What was the gas volume before the plunger was moved?
- A$0.25\,\text{cm}^3$
- B$40\,\text{cm}^3$
- C$63\,\text{cm}^3$
- D$160\,\text{cm}^3$