The depth (in feet) of water at a dock changes with the rise and fall of tides. The depth is modeled by the function D(t), where t is the number of hours after midnigh D(t) = 7 sin(t-77)+ +3 6 6 Find the rate (in ft/hr) at which the depth is changing at 5 a.m. (Round your answer to one decimal place.) t ft/hr