Final answer:
The top of the tallest building in the city is 12,064.5 feet above sea level.
Step-by-step explanation:
To calculate the height of the tallest building above sea level, we need to add the height of the tallest building to the depth below sea level where Cameron is standing.
The tallest building is 12,000 feet high and Cameron is 64.5 feet below sea level. To find the total height above sea level, we add:
12,000 feet + 64.5 feet = 12,064.5 feet
Therefore, the top of the tallest building in the city is 12,064.5 feet above sea level.