please explain

A first class lever has a di of 42 cm and a de of 126 cm. To keep the lever in static equilibrium, an effort force of 52 N is required to balance the 12 kg load (hint some force is lost when your lever bends under the stress). Calculate: 1. IMA (2 marks) 2. AMA (3 marks) 3. % Efficiency (2 marks)