Algebraic varieties named for this shape are subject to the orbit–cone correspondence and can be constructed from fans. For knots named for this shape, “x-to-the-p equals y-to-the-q” is a relation of the knot group. “R-squared” quotient “Z-squared” is isomorphic to this surface, which has “Z-cross-Z” as its fundamental group. (10[2])This surface can be obtained (10[1])by gluing each pair of opposite edges of the unit square (10[1])in the same direction. This orientable surface with Euler characteristic zero is the Cartesian product of two circles. Depending on orientation, either a Klein bottle or this genus-one surface (-5[1])is formed by joining the circular ends of a cylinder. (10[1])For 10 points, the surface of a coffee cup is topologically equivalent to what single-holed (10[1])surface shaped like a doughnut? ■END■