A 250 mL waste water sample is collected. 100 mL of 0.25 N K2Cr2O7 is added to the water sample as well as to a separate 250 mL sample of distilled water. Both samples are heated to 50°C for 30 minutes. The samples are allowable to cool for 10 minutes and then titrated with 1.500 N iron (II) ammonium sulfate. The waste water sample needs 28.51 mL of titrant, while the blank sample needs 44.37 mL to reach a 1, 10 phenanthroline endpoint. Explain what the COD of the waste water sample is