A fixed mass of gas is contained within a sealed syringe at a pressure of 100 kPa. The plunger is slowly moved until the pressure is 80 kPa. The final volume of the gas is 50 cm^3. The temperature of the gas does not change.
What is the volume of the gas before the plunger is moved?
A) 0.25 cm^3
B) 40 cm^3
C) 63 cm^3
D) 160 cm^3