13. The concentration of a certain drug, in mg/L, can be modeled by the following function: C(t)=5te, 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. (A) (0,0.31) (B) (3.26,00) (C) (0,) (D) (0.31,) (E) (0.31,3.26)