What is an air mass and what determines its properties

On his honeymoon, james joule attempted to explore the relationships between various forms of energy by measuring the rise of temperature of water which had fallen down a waterfall on mount blanc. what maximum temperature rise would one expect for a waterfall with a vertical drop of 20 m? the specific heat of water is 4186 j/kg ∙ k. a)0.064 c° b)0.053 c° c)0.071 c° d)0.047 c°