(907, #39) A 160-lb man carries a 25-lb can of paint up a helical
staircase that encircles a silo with a radius of 20 ft.
If the silo is 90 ft high and the man makes exactly three
complete revolutions, how much work is done by the man against gravity
in climbing to the top?
Solution: Here is a graph of the helical staircase.
Let 
We can parameterize the staircase with:
Maple code
by C.A.H.