Calculating net force

0N.

Explanation:

Net force is the sum total of forces acting on an object.

The Fn which is the net force is

450+ (-250) + (-600)+ 600+ 0 + 250 + (-450)

= 450-250+(-600)+ 600+0+250-450

= 0N

The net force is 0

c because the action was the roller coaster reaches bottom of hill (action) reaction would be blood tends to drain away from head

hope this !