Answer:

The farthest point is the Challenger Deep
Step-by-step explanation:
Given


Solving (a): The sea level
Both elevations had signs in front of them.
The sea level is the point at the neutral level, neither positive nor negative.
Hence:

Solving (b): Farthest Point.
The farthest point is the one with the highest magnitude.
Comparing
to 
-35,797 ft has the highest magnitude.
Hence:
<em>The farthest point is the Challenger Deep</em>