A group of EPA scientists collect 1000 water samples from drinking water. They test those samples for a certain chemical. The test is not 100%...

A group of EPA scientists collect 1000 water samples from drinking water. They test those samples for a certain chemical. The test is not 100% correct. If the sample contains the chemical, the test shows a positive result 96% of the time. If the sample does not contain the chemical, it gives a negative result 93% of the time. If 200 groundwater samples contain chemicals, what is the probability the sample contains a chemical if you have a positive test return for the sample?