An antibiotic is attacking a bacterial infection so quickly that the number of bacteria is exponentially decreasing continuously. Originally there were 2 million bacteria and now there are 0. 5 million bacteria. Using k = 0. 05 for the hourly rate of decay, how many hours did it take to its current level?
about 13. 9 hours
about 9. 9 hours
about 16. 6 hours
about 27. 7 hours
