Air in an ideal Diesel cycle is compressed from $3 \: \mathrm{litre}$ to $0.15 \: \mathrm{litre}$. It then expands during a constant pressure heat addition process to $0.3 \: \mathrm{litre}$. If the ratio of specific heats, $\gamma=1.4$, the thermal efficiency (in $\%$ ) of the cycle is $\_\_\_\_\_\_\_$ (rounded to one decimal place).
