Dear Student,
Please find below the solution to your problem.
Ideal gas equation is PV=nRT.
Initially T = 121 + 273 = 394k
so PV = nR(394)....(1)
After since 1/4 of the gas is escaped so
n`=n-1/4n =3n/4
so PV=(3n/4)RT`....(2)
now equating equations we get
nR394=3n/4RT`
we get T`=525k
=252`c
here v remains same because the remaining gas also occupies whole of the container volume.(since gas have infinite expandability).
Thanks and Regards