An auto assembly plant performs six functions with each frame that arrives: add axles, add wheels to the axles, install the windshield to the frame, install the instrument panel, install the steering wheel, and install the interior seating. Once those six tasks are performed, each car goes to a separate building for finishing touches. If these tasks can be arranged along a linear assembly line in any order, except that the axles must be installed before the wheels can be added, how many E ways can the assembly line be arranged? Choose one.
A) 120
B) 240
C) 360
D) 480
E) 720
C) 360   short way: there are 6C! ways to do the six tasks. Half will have wheels before axles and half will have axles before wheels. So we want E=6360!/2 -&gt; 720/2 = 360
<result>C</result>
An auto assembly plant performs six functions with each frame that arrives: add axles, add wheels to the axles, install the windshield to the frame, install the instrument panel, install the steering wheel, and install the interior seating. Once those six tasks are performed, each car goes to a separate building for finishing touches. If these tasks can be arranged along a linear assembly line in any order, except that the axles must be installed before the wheels can be added, how many E ways can the assembly line be arranged?