I need help, with this Bio chemistry problem. Please, explain...

To analyze the B chain, Dr. Sanger carried out the following steps: 1. Oxidized insulin to separate the A and B chains. 2. Prepared a sample of pure B chain with paper chromatography. 3. Reacted the B chain with FDNB. 4. Gently acid-hydrolized the protein so that some small peptides would be produced. 5. Separated the DNP peptides from the peptide that did not contain the DNP groups. 6. Isolated four of the DNP-peptides, which where named B1 through B4. 7. Strongly hydrolyzed each DNP-peptide to give free amino acids. 8. Identified the amino acids in each peptide with paper chromatography. The results were as follow: B1:DNP-phenylalanine only B2: DNP-phenylalaine ,valine B3, Aspartic acid, DNP-phenylalanine, valine B4: Aspartic acid, glutamic acid, DNP-phenylalanine, valine c) Based on these data, what are the first four (amino-terminal) amino acids of the B chain ? Explain your reasoning. d) Does this match the known sequence of insulin? Explain any discrepancies. A chain B chain NH, NH Gly Phe lle Val Val Aen Glu 8 Gin 6 His Cys Leu Cys S S Cys s Ala Gly Ser S Ser 10 Val 30 His 1 Leu -Cys Ser Val Leu Glu Ala Gin 15 18 Leu Leu Tyr Leu Glu Aan Val Tyr Cys Gly > Cys S 30 Asn Glu COO Arg Gly Phe Phe Tyr Thr Pro 1 Lys 30 Ala 000