A hydraulic system operates a dentists' chair. At one end of the hydraulic line there is a circular piston of radius r1=30 cm that supports the chair. The weight of the chair (with the patient in it) is 3000N. At the other end of the hydraulic line there is a smaller circular piston (r2=3 cm) that the dentist pushes down in order to lift the chair. What is the force that the dentist has to apply to the small piston?