To help Serena adjust to the new time zone, Rebecca should: offer her a dose of melatonin.
Melatonin is a hormone, secreted by the pineal gland in the brain. Melatonin is found in some foods and it is also available as a pill. Melatonin performs various roles in the body. It is involved in the sleep/wake and reproductive cycles in humans. The secretion and release of melatonin in the brain has to do with time of day. It decreases when it is light and it increases when it's dark. The secretion of melatonin in the brain reduces with age.
