Charles and Maggie are fighting and tugging over Maggie's stuffed animal. Charles pulls with a force of 15 N to the left. Maggie is pulling with a force of 7 N to the right . Their dog, Max, hears Maggie crying over the stuffed animal and intervenes and tugs on the toy to the right with Maggie. It is now a fie - all of the external forces are at equilibrium . How much force would Max need to pull with to put these forces at equilibrium ?