Answer:
10,620
Explanation:
Since it reached a height of 10,400 before exploding and was 220 feet below sea level we need to add the two numbers together to get the total change in altitude.
You can think of it as sea level = 0 so 220 feet below sea level is -220 and 10,400 above sea level is +10,400 so what's the difference between the two.
Finding the Difference
10400 - (-220)
= 10400 + 220
= 10620