The quantity of oxygen that can dissolve in water depends on the temperature of the water. (So thermal pollution influences the oxygen content of water.) The graph shows how oxygen solubility S varies as a function of the water temperature T. (a) What is the meaning of the derivative S '(T)?
S '(T) is the rate at which oxygen solubility changes with respect to the water temperature.
S '(T) is the rate at which temperature changes with respect to the temperature.
S '(T) is the rate at which temperature changes with respect to the oxygen solubility.
S '(T) is the rate at which oxygen solubility changes with respect to the oxygen solubility.
S '(T) is the current level of oxygen solubility for a given temperature.

(b) Estimate the value of S '(32). (Round your answer to three decimal places.)
S '(32) ≈
(mg/L)/°C