In a ground water contamination study, the researchers identify 25 possible sites for drilling and sample collection. Unknown to the researchers. 19 of these sites have ground water with a high contamination, while the other 6 sites have ground water with a low contamination. The researchers have a budget that only allows them to drill at 5 sites, so they randomly choose these 5 sites from their list of 25 sites. What is the probability that at least 4 out of the 5 sites that the researchers examine have ground water with a high contamination?