The tetrapeptide Trp-Arg-Phe-Glu at pH 7 was digested with trypsin and then fully deprotonated by adjusting to pH=14. The digestion products were then applied to a strong anion exchange column (positively charged). The peptides were then eluted from the column using a pH gradient from 14 to 0.5. Write the primary amino acid sequence of the products (full structures not required) in the order they would elute from the column. Indicate the pH value at which each product elutes from the column. Assume pKa's for any newly generated a-amino and a-carboxyl groups are 9.5 and 2.1, respectively.