Some of the highest tides in the world occur in the Bay ofFundy on the Atlantic Coast of Canada. At Hopewell Capethe water depth at low tide is about 2.0 m and at high tideit is about 12.0 m. The natural period of oscillation is alittle more than 12 hours and on June 30, 2009, high tideoccurred at 6:45 AM. This helps explain the following modelfor the water depth D (in meters) as a function of the time(in hours after midnight) on that day: D(t) = 7+ 5cos [0.503(t -6.75)])How fast was the tide rising (or falling) at the followingtimes?(a) 3:00 AM (b) 6:00 AM(c) 9:00 AM (d) Noon

Some of the highest tides in the world occur in the Bay of
Fundy on the Atlantic Coast of Canada. At Hopewell Cape
the water depth at low tide is about 2.0 m and at high tide
it is about 12.0 m. The natural period of oscillation is a
little more than 12 hours and on June 30, 2009, high tide
occurred at 6:45 AM. This helps explain the following model
for the water depth D (in meters) as a function of the time
(in hours after midnight) on that day:

D(t) = 7+ 5cos [0.503(t -6.75)])
How fast was the tide rising (or falling) at the following
times?
(a) 3:00 AM (b) 6:00 AM
(c) 9:00 AM (d) Noon