he following precedence network is used for assembling a product. You have been asked to achieve an hourly output of 20 units. All times in this network are in minutes. What is the actual number of workstations after balancing the line

answer; defense;

only #2 represents an object at rest on a table.

in #1, there is no normal force due to the table; the object is accelerating downward.

in #3, the vertical forces are not balanced; the object is accelerating downward.

in #4, neither the vertical nor the horizontal forces are balanced. the object is accelerating upwards and to the right.