21. When a person lifts himself on the toes, the calf muscles act as a second class lever, and the moment arm distances are as shown. If the person weighs 200 lb. and the body weight is equally distributed between the two feet, the force F the calf muscle will exert should be: A) 100 1b. B) 167 1b. C) 60 1b. D) 120 1b.21. When a person lifts himself on the toes, the calf muscles act as a second class lever, and the moment arm distances are as shown. If the person weighs 200 lb. and the body weight is equally distributed between the two feet, the force F the calf muscle will exert should be: A) 100 1b. B) 167 1b. C) 60 1b. D) 120 1b