A Pure Culture in Exponential Growth Phase Has a Bacterial

A pure culture in exponential growth phase has a bacterial concentration of 6.4 × 108 cells/ml. If the bacterium has a generation time of 1 h, how long ago was the cell concentration 8.0 × 107 cells/ml?

A) 1 h
B) 2 h
C) 3 h
D) 4 h
E) 24 h