The gas reached a pressure of 2.5 atm.
Since the volume is constant but the pressure and temperature are changing, this is an example of Gay-Lussac's Law:
#color(blue)(bar(ul(|color(white)(a/a) P_1/T_1=P_2/T_2color(white)(a/a)|)))" "#
We can rearrange the above formula to get
#P_2=P_1 × T_2/T_1#
Your data are:
The new pressure is 2.5 atm.