An oil-storage area was abandoned 18 years ago. Oil spilled on the ground had saturated the soil at a concentration of 400mg/Kg of soil. A fast food chain now wants to build a restaurant at the site, and samples the soil for contaminant, only to discover that the soil still contains oil residue at a concentration of 20mg/kg. You are consulted as the expert environmental engineer on biodegradation of oil spill to give advice. Having identified the microorganism involved the biodegradation and discovered that its mode of action is zero-order reaction with a reaction rate of 20 mg/kg-year, you concluded that in one more year the site will be free of all contamination.