

Jim is surveying the height of two rocks
in Death Valley. After the measurement, he finds that one is
6 feet below sea
level,
and the other is about 100 feet above sea level. When
he moves from the first rock to the second, he notices that elevation,
s, is a function of time: s = t^{2} 
t  6. Jim wondered how many times he passed through the sea
level
during
his
travel.
The
distance unit is feet and
the time unit is minute.
What is known:
 The elevation function is:
 One rock is 6 feet below sea level, the other rock is 100
feet above sea level.
