How many atmospheres of pressure must a litre of gas, initially at a pressure of 1 atmosphere and temperature -20°C, be after it has been compressed to 1/2 litre at 40°C?

• A.2.47 atm.
• B.4.5 atm.
• C.8.0 atm.
• D.3.8 atm. (E) 16.8 atm