Critical temperature and liquefaction of gases

2022 Phase 2 1 question

1. Four gas cylinders containing He, $N_2$, $CO_2$ and $NH_3$ gases separately are gradually cooled from a temperature of 500 K. Which gas will liquify first? (Given $T_c$ in K - He: 5.3, $N_2$: 126, $CO_2$: 304.1 and $NH_3$: 405.5)