Hello, Christion,
Use the Ideal Gas Law in the form P1V1/T1 = P2V2/T2, where the 1 and 2 represent the initial and final states. Nothing is said about the temperature, so assume it stays constant and the T1 and T2 cancel out. Rearrange the equation to a P2 = format and then plug in the numbers. I see a decrease in pressure to 5.37 atm. Does this make sense? We didn't add any gas and the temperature remained the same. The only way to increase the volume would be to reduce the pressure.
I hope this helps, Bob