(***) The concentration of a certain drug, in mg/L, can be modeled by the following function: C(t)= 5t · e0.81 , where t is the number of hours after the drug was administered. The drug is effective...

Extracted text: (***) The concentration of a certain drug, in mg/L, can be modeled by the following function: C(t)= 5t · e0.81 , where t is the number of hours after the drug was administered. The drug is effective if its concentration is greater than 1.2 mg/L. Use the graph of the function to determine the interval of time when the drug is effective.