A sample of bacteria taken from a river has an initial concentration of 2.6 million bacteria per milliliter and its concentration doubles each week. (a) Find an exponential model that calculates the concentration (in millions) after x weeks. (b) Estimate the concentration (in millions) after 1.1 weeks. (a) B(x) = (Type an equation using x as the variable.) (b) The estimated concentration of bacteria after 1.1 weeks is million per milliliter. (Round to the nearest integer as needed.)