4.II.11G

Groups, Rings and Modules
Part IB, 2007

A regular icosahedron has 20 faces, 12 vertices and 30 edges. The group GG of its rotations acts transitively on the set of faces, on the set of vertices and on the set of edges.

(i) List the conjugacy classes in GG and give the size of each.

(ii) Find the order of GG and list its normal subgroups.

[A normal subgroup of GG is a union of conjugacy classes in GG.]