Two people are pushing inward on a door from the outside. One person is pushing the door shut from the inside. The first individual pushing outside is pushing in with a 500N force right in the middle of the door. The second individual is pushing inward with a 400N force only 12 cm away from the door's hinged-side. The door is 90cm wide and the individual inside is pushing the door near the edge opposite of the hinges.
a. How strong a force will the single individual on the inside need to keep the door from opening?
b. If the indoor indivual pushes with the force in part a., how much force is the hinge exerting on the door?