A water sample was analyzed to determine the concentration of bacteria in it. It was diluted as follows: 1ml of sample placed in 9ml of sterile water (tube A) from this solution, from that another 1ml was placed in 9ml of sterile water (tube B) and from that 1ml was placed in another 9ml of sterile water (tube C). Spread plates were then made by taking 1.0ml and 0.1ml from the last two tubes. The places were incubated and the results are tube C having 260 CFU from the 0.1 ml volume transfered. Determine the concentration of bacteria.