Answer:
15,211 feet
Explanation:
According to the question, given data are as follows:
Airplane altitude = 14,690 feet above
Submarine depth = 521 feet below
So, let the difference between these two elevation be d,
So, we can calculate difference by using following formula:
Difference = Airplane altitude + Submarine depth
By putting the value, we get
Difference = 14,690 + 521
= 15,211 feet