The concentration of the contaminant in the lake is given by formula
C(t) = 60(1 - e-0.0345t), where C is in mg/liter and t is in days. Effluent entering lake will be shut down, pending an EPA review, when concentration of the contaminant reaches 25 mg/liter, After how many days, correct to nearest whole day, will concentration, in mg/liter, reach the level?