A colony of Escherichia coli is inoculated from a Petri dish into a test tube containing 50 of nutrient broth. The test tube is placed in a 37 deg * C incubator and agitator. After one hour, the number of bacteria in the test tube is determined to be 8 * 10 ^ 6 Given that the doubling time of Escherichia coli is 20 minutes with agitation at 37 deg * C approximately how many bacteria should the test tube contain after eight hours of growth?