A BOD test is run with 150 mL of wastewater mixed with 150 mL of deionized…

A BOD test is run with 150 mL of wastewater mixed with 150 mL of
deionized water. The initial DO = 8.5 mg/L, the DO after 5 days =
4.2 mg/L, and the DO ultimately levels off at 1.7 mg/L. Assume all
nitrification has been inhibited and the temperature remains
constant.
a) Calculate the CBOD5 (y5, mg/L)
b) Calculate the ultimate CBOD (Lo, mg/L)
c) Calculate the CBOD remaining after 5 days (L5, mg/L)
d) Calculate the deoxygenation rate constant (kL, day^-1)
PS: I think this is a Determonation of Sturation DO
Concentration question. I am not sure 100%