Department of Mathematics, Davidson College, NC, USA. laheyer@davidson.edu|Department of Mathematics, Davidson College, NC, USA. laheyer@davidson.edu|Department of Mathematics, Davidson College, NC, USA. laheyer@davidson.edu|Department of Mathematics, Davidson College, NC, USA. laheyer@davidson.edu|Department of Mathematics, Davidson College, NC, USA. laheyer@davidson.edu|Department of Mathematics, Davidson College, NC, USA. laheyer@davidson.edu|Department of Mathematics, Davidson College, NC, USA. laheyer@davidson.edu|Department of Mathematics, Davidson College, NC, USA. laheyer@davidson.edu