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anti - an IVI an) an 6. A certain drug is effective in treating a disease if the concentration remains above 100 mg/L. The initial concentration is 640 mg/L. It is known from laboratory experi- ments that the drug decays at the rate of 20% of the amount present each hour. a. Formulate a model representing the concentration at each hour. b. Build a table of values and determine when the concentration reaches 100 mg/L. T