For a reversible adiabatic process :
T1Vγ−11=T2Vγ−12
Given, T1 =300 K
V2=64V1
putting the values we get,
⇒300×V1/31=T2(64V1)1/3T2=75 K
So, final temperature is 75 K
and work done will be ,
W=nCv(T2−T1)
we know Cv=Rγ−1
so,
W=1×Rγ−1(75−300)=243−1(−225)=−1350 cal