A 1.00 102 m3 flask contains 0.0160 kg of oxygen gas, O2, at 77.0 C. What is the pressure exerted on the inner walls of the flask by the oxygen gas? Note: the atomic mass of O is 15.9994 u

Answer is 1.45 x 10^5 Pa according to my answer key. I got 2.9 x 10^5 Pa. I can see that is half of the answer that I got, not sure if that is coincidental or not. If the answer is for some reason just half of the answer that i got, can you explain why? Or just help with the work if it is coincidental.