Answer: 19,960,039.97 days
Explanation: f(t) = 200e0.002t
where, f(t) is number of bacteria in millions and t is time in days.
so, if the product cannot be eaten after the bacteria count reaches 4000, it will take:
4,000,000,000 = 200e0.002t
4,000,000,000 = 200.4004003t
therefore, t= 4,000,000,000/200.4004003 =19,960,039.97 days
that is, to say that it will take 19,960,039.97 days before the product will not be eaten again.