

Step $1$ It is first compressed adiabatically from volume $V_{1}$ to $1 \;m ^{3}$.
Step $2$ Then expanded isothermally to volume $10 \;m ^{3}$.
Step $3$ Then expanded adiabatically to volume $V _{3}$.
Step $4$ Then compressed isothermally to volume $V_{1}$. If the efficiency of the above cycle is $3 / 4$, then $V_{1}$ is ............ $m^3$
Step $1$ It is first compressed adiabatically from volume $8.0 \,m ^{3}$ to $1.0 \,m ^{3}$.
Step $2$ Then expanded isothermally at temperature $T_{1}$ to volume $10.0 \,m ^{3}$.
Step $3$ Then expanded adiabatically to volume $80.0 \,m ^{3}$.
Step $4$ Then compressed isothermally at temperature $T_{2}$ to volume $8.0 \,m ^{3}$.
Then, $T_{1} / T_{2}$ is
