PLEASE HELP ME Physics Static Equilibrium Problem!?

The anatomical structures in the lower leg and foot that are involved in standing on tiptoe, with the heel raised slightly off the floor so that the foot effectively contacts the floor only at point P. Assume distance a= 5.0 cm, distance b=15 cm, and the person's weight W= 900 N. Of the forces acting on the foot:


What are the:


(a) Magnitude of the force at point A from the calf muscle


(b) Direction of the force at point A from the calf muscle (up or down)


(c) Magnitude of the force at point B form the lower leg bones


(d) Direction (up or down) of the force at point B form the lower leg bones?





Answers:


(a) 2.7 kN


(b) Up


(c) 3.6 N


(d) Down





I don't know how they got these answer so if you can please show how.

PLEASE HELP ME Physics Static Equilibrium Problem!?
A diagram would have helped.





I derived the following diagram:





A%26lt;---a---%26gt;B%26lt;----b---%26gt;P





Evaluate the torques:





There is a torque at point P of the weight of the person pushing upward against the foot. The sum of the torques about any point must equal 0.





Sum the torques at point B:





A*5-900*15=0


A=2700





The direction is up to counter act the torque at P





for (c), I get 3600 N, or 3.6 kN as follows:





2700+900=3600N since downward forces must equal the sum of upward forces.





The weight of the person I assumed was centered at B.





Also using torque summed about point A





900*20-B*5=0


B=3600N





Also, check the torque about point P


2700*20-B*15=0





B=3600N





It all checks, I hope I had the diagram correct.





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