The bacterially produced antibiotic gramicidin A forms channels in cell membranes that allow the free diffusion of Na and K ions, thereby killing the cell. This peptide consists of a sequence of D- and L-amino acids. The sequence of a segment of five amino acids in gramicidin A is R-Gly-L-Ala-D-Leu-L-Ala-D-Val-R¿. Complete the Fischer projection below by adding the correct group to each vertical bond.