A mechanic standing on a hydraulic lift supports three 120 kg motorcycles at a height of 1.2 m above the mechanic's piston. The hydraulic lift is filled with oil, and the mechanic's piston has a radius of 6 cm. Calculate the radius of the piston lifting the motorcycles if the mechanic's mass is 72 kg. Assume that oil has a density of 900 kg/m³.