An environmental monitoring station tracks water salinity levels (in parts per thousand, ppt) across several estuarine research zones to protect a sensitive fish species. If a zone's salinity falls outside the safe range, marine biologists must be immediately alerted.

• The ideal salinity for the fish species is $15ppt$.
• The permissible salinity tolerance is plus or minus four parts per thousand (an inclusive range of $11ppt$ to $19ppt$).
• Only zones with salinity levels strictly outside this tolerance (less than $11ppt$ or greater than $19ppt$) are considered critical.
• An output message must be displayed to show the index and salinity of any zone that is critical.
• The output message for each critical zone must be on a single line.
• No other messages should be displayed.
• A global data structure holding the salinity measurements is provided and must be used as part of the solution:

SET zoneSalinity TO [15, 12, 9, 21, 19, 22, 11]

• The solution should work even if the number of zones in the data structure is changed.

An example output for the dataset above is shown:

Zone 2 is critical: 9 ppt
Zone 3 is critical: 21 ppt
Zone 5 is critical: 22 ppt