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subtract2 - subtracts cylinder 3 from cylinder 1 creating a hollow pipe coming out of the page.
cylinder5 - creates a cylinder that will form the outer wall of pipe 3with a depth 'H' and radius 'R3' into the page.
cylinder6 - creates a cylinder that will form the inner wall of pipe 3with a depth 'H' and radius 'R1' into the page.
subtract3 - subtracts cylinder 6 from cylinder 5 creating a hollow pipe with length 'H'.
viewfront - sets the workspace so that the user is viewing the object from the front.
mirror1 - mirrors the bottom pipe 90 degrees clockwise.
mirror2 - mirrors the bottom pipe 180 degrees.
bigunion1 - joins the third, forth and fifth all four pipes.mirror3 -