Answer:
Horizontal displacement = 100 km
Position with respect to sea level = -0.4km
Step-by-step explanation:
Let the displacement downwards be negative displacement and displacement upwards be positive.
The horizontal distance from the shore remains constant whereas the displacement from the sea level varies as the submarine moves.
The upward displacement = 3/5 km
Downward displacement = - 1/10 km and - 9/10 km
Total displacement = 3/5km - 1/10 km - 9/10km = - 2/5 km = - 0.4 km
Horizontal distance from the shore = 100km