Show that a directed multigraph having no isolated vertices has an euler circuit if and only if the graph is weakly connected and the in-degree and out-degree of each vertex are equal

1. explain how you calculate the net force in any direction on the box. 2. suppose an upward force of 15n is added to the box. what will be the net vertical force on the box? 3. what force could be applied to the box to make the net force in the horizontal direction zero? explain. 4. suppose a force of 25n to the right is added to the box. what will be the net force to the right?