Taking the ground-state ionisation energy of hydrogen as 13.6 eV, select the correct statements.

1. AThe ratio of the ionisation energy of $\mathrm{Li}{}^{2+}$ to that of $\mathrm{He}{}^{+}$ is 3
2. BThe ionisation energy of $\mathrm{He}{}^{+}$ is 54.4 eV
3. CThe ionisation energy of $\mathrm{Be}{}^{3+}$ is 16 times that of $\mathrm{H}$
4. DThe ionisation energy of $\mathrm{Li}{}^{2+}$ is 122.4 eV