A paddle wheel frictionally adds thermal energy to an ideal monatomic gas in a sealed, insulated container. The paddle wheel is driven by a cord connected to a falling object as shown in the drawing. In this experiment, a 5.0-kg object falls through a total distance of 2.0 m and the temperature of the gas is found to increase by 4 C°. Assume that all of the mechanical energy lost by the falling object goes into the gas. How many moles of gas must be present in this container?