With regard to the take-off performance of a twin jet aeroplane, why does the take-off performance climb limit graph show a kink at 30°C and PA 0'?

Question

Question ATPL - Airline Transport Pilot license - Performance

QuizVDS · Accepted Answer

The engines are pressure limited at lower temperature, at higher temperatures they are temperature limited[see Annex]

QuizVDS · Answer

At lower temperatures one has to take the danger of icing into account

QuizVDS · Answer

At higher temperatures the VMBE determines the climb limit mass

QuizVDS · Answer

At higher temperatures the flat rated engines determines the climb limit mass

Id 21 - ATPL - With regard to the take-off performance of a twin jet aeroplane, why does the take-off performance climb limit graph show a kink at 30°C and PA 0'?