==> geometry/K3,3.p <==
Can three houses be connected to three utilities without the pipes crossing?

            _______          _______          _______
            | oil |          |water|          | gas |
            |_____|          |_____|          |_____|


            _______          _______          _______
            |HOUSE|          |HOUSE|          |HOUSE|
            | one |          | two |          |three|