To reduce laboratory? costs, water samples from twotwo public swimming pools are combined for one test for the presence of bacteria. further testing is done only if the combined sample tests positive. based on past? results, there is a 0.0070.007 probability of finding bacteria in a public swimming area. find the probability that a combined sample from twotwo public swimming areas will reveal the presence of bacteria. is the probability low enough so that further testing of the individual samples is rarely? necessary?