The Moon has a mass of 7.36 * 10^22 kg.  It is 3.84 * 10^8 m away from the center 
of the Earth.  Earth's radius is 6,378,000 meters.

   (a) At what rate does the Moon gravitationally accelerate the part of 
       Earth's surface closest to it?  (For this problem, keep careful track
       of many decimal places; the details are important in this instance.)
   (b) At what rate does the Moon gravitationally accelerate the part of 
       Earth's surface farthest away from it?
   (c) What is the difference between these two rates of acceleration?
       How does that net difference - what we might loosely call the
       "tidal differential" - compare to the gravitational acceleration
       of Earth at its surface, 10 meters per second squared?