In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

Example Input: Masturbation tends to peak when children are between the ages of _ and five.
Example Output: three

Example Input: Plasma levels fall by about a half within three to _ hours.
Example Output: four

Example Input: Trees can withstand extended drought, and up to _ months of inundation.
Example Output:
six