The speed of sound traveling through water with salinity 35 parts per thousand has been modeled by the equation $C = 1449.2 + 4.6T - 0.055T^2 + 0.000292T^3 + 0.016D$ where C is the speed of sound (in meters per second, T is the temperature (in degrees Celsius) and D is the depth below the ocean's surface (in meters). For a recreational diver we have graphs of the temperature of the water and depth of the diver at time t. Estimate the rate of change of the speed of sound through the ocean water at time t = 30 minutes.

Temperature

Depth

ANS: .