Answer: Prefrontal cortex
Step-by-step explanation:
Prefrontal cortex is the region of brain which present in front part. It's function is to perform decision making, addressing complex behavior, impacting social behavior and mind, planning expression of personality etc.Therefore, it manipulates and processes congnitive behavior.
According to the question, Rebecca's organizing personality for ordering her tasks like studying,eating etc is based on mature prefrontal cortex.It helps in regulating tasks and planning the cognitive tasks.