A Paddle Wheel Frictionally Adds Thermal Energy to an Ideal

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 3.0 m and the temperature of the gas is found to increase by 6 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?

A) 2.0
B) 3.0
C) 4.0
D) 5.0
E) 6.0