An oil storage area, abandoned 19 yr ago, had spilled oil on the ground and saturated the soil at a concentration of perhaps 400 mg/kg of soil. a fast food chain wants to build a restaurant there and samples the soil for contaminants only to discover that the soil still contains oil residues at a concentration of 20 mg/kg. the local engineer concludes that, since the oil must have been destroyed by the soil microorganisms at a rate of 20 mg/kg each year, in one more year the site will be free of all contamination. a. is this a good assumption? why or why not? (hint: consider kinetics.) b. how long would you figure the soil will take to reach the acceptable contamination of 1 mg/kg?