(a) The relationship between photon index |$\Gamma$| and total luminosity |$L_\mathrm{X}$| during the 2018 outburst. Blue dots, green dots, red dots, green triangles, and blue triangles, respectively indicate rising hard state and intermediate state, soft state, decaying hard state, and intermediate state. The black stars mark the transition luminosities between HS and IMS in the outburst rise and decay phases. Arrows indicate the direction of evolution. (b) The relationship between the ratio of Comptonization luminosity |$L\mathrm{_{C}}$| to seed photons luminosity |$L\mathrm{_{seed}}$| and total luminosity |$L_\mathrm{X}$| during the 2018 outburst. Symbols and colours are the same as in panel (a).