9. A particular running experiment is initially 100 bacteria cells. She expects that the number of cells is given by the function c(t) = 100(2)t/15, where time t is the number of hours since the experiment started. After how many hours would the scientist expect to have 500 bacteria cells? Give your answer to the nearest hour.
A 24 hours B. 30 hours C. 35 hours D. 42 hours​