Answer:

Step-by-step explanation:
Given
Initial Level = 340 m
Number of stages = 4
Difference in each stage = 60 m
Required
Determine the depth of the submarine after 4 stages
First, we have to calculate the total distance moved towards the surface of the sea;
This is calculated as



This implies that the submarine moved a total distance of 240 metres;
It;'s new depth is calculated as follows;



<em>Hence, its new depth after 4 stages of rising is 100m</em>