Environmental Engineering An article in the Journal of the Environmental Engineering Division ("Distribution of Toxic Substances in Rivers," Vol 108, 1982 pp.639-649) describes a study of the concentration of several hydrophobic organic substances in the Wolf River in Tennessee. Measurements of hexachlorobenzene (HCB) in nanograms per liter were taken at different depths downstream of an abandoned dump site. Data for two depths are as follows: Surface: 3.74, 4.61, 4.00, 4.67, 4.87, 5.12, 4.52, 5.29, 5.74, 5.48, 5.10, 4.95 Bottom: 5.44, 6.88, 5.37, 5.44, 5.03, 6.48, 3.89, 5.85, 6.85, 7.16, 5.70, 4.50b) Determine the critical value and label it. (example, z = 1.96 ort = -2.421, etc). t = 1.380 c) Compute the test value, z or t. If you are using the p-value method, then compute the test value and include the p-value of the test (4 decimal places). t= -2.92 p-value = 0.0020 d) Make the decision to Reject Ho or Do not reject Ho. Reject Ho e) State your complete conclusion in the context of the claim. We can conclude that the data shows there is sufficient evidence to support the claim that the mean HCB concentration is different in different depths of the river.Surface - Mean: 4.84 Median: 4.91 Standard Deviation: 0.33 Bottom - Mean: 5.72 Median: 5.57 Standard Deviation: 0.99