7. A batch reactor operates at first order for one contaminant (contaminant X) and zero orderfor another contaminant (contaminant Y). The starting concentration of both contaminantsIs 100 mg/L and both

are degraded. The zero order reaction rate constant k=2 mg/(L day)and the first order reaction rate constant k - 0.1/day. At which of the following times willthe concentration of the two contaminants be the same? Shortly before t-20 daysShortly before t=50 daysShortly before t-100 daysd) Shortly before t=1000 dayse) Concentrations will never be the same