The disaccharide at the terminus of the oligosaccharide attached to the surface of type B red blood cells is an α-D-galactopyranosyl-β-D-galactopyranose. The linkage is an acetal from C1 of the first galactose to the C3 hydroxy group of the second. In other words, the full name is 3-(β-D-galactopyranos-l-yl)-β-D-galactopyranose. Draw the structure of this disaccharide, using conformationally accurate chairs for the six-membered rings.