Agroup of asu sustainability student took 100 soil samples in different places in the valley. they test those samples for a certain chemical. the test is not 100% correct. if the soil contains the chemical, the test shows a positive test result 90% of the time. if the soil does not contain the chemical, it gives a negative result 80% of the time. if 20 of the soil samples contain chemicals, what is the probability the sample contains a chemical if you have a positive test return for the sample?