A reaction $\mathrm{R}\to \mathrm{I}{}_1\to \mathrm{I}{}_2\to \mathrm{P}$ has relative energies (kJ/mol): R = 0, TS1 = 60, I1 = 25, TS2 = 90, I2 = 40, TS3 = 55, P = $-20$. Which statements are correct?

1. AThe activation energy of the step $\mathrm{P}\to \mathrm{I}{}_2$ is 15 $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
2. BThe reaction has two intermediates
3. CThe overall $\Delta H$ is $-20\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$
4. DThe rate-determining step is $\mathrm{I}{}_1\to \mathrm{I}{}_2$