Answer
At the top of the mountain, you'll age faster.
Work Step by Step
Strong gravitation expands time intervals, i.e., it slows down the passage of time.
The biological clock on the mountain is farther from the center of the Earth than the clock at ground level, so it is in a weaker gravitational field and will run more quickly.
This is discussed on pages 691-692, and shown in Figure 36.10.