40% of HI undergoes decomposition to H₂ and I₂ at 300 K. $\Delta$G$^\Theta $ for this decomposition reaction at one atmosphere pressure is __________ J mol^$-$1. [nearest integer]

(Use R = 8.31 J K^$-$1 mol^$-$1 ; log 2 = 0.3010, ln 10 = 2.3, log 3 = 0.477)