(i) Plane Groups: Consider plane groups with a square lattice:
(a) Derive the p4 plane group by adding the4 (C4) point group to a lattice point. List the equipoints, site symmetries and multiplicities.
(b) Derive the p4mm plane group by adding the 4mm (C4y) point group to a lattice point. List the equipoints, site symmetries and multiplicities.