The insecticide DDT has a half-life in the human body of approximately 7 years. That is, in 7 years its concentration. Although DDT is no longer in...

The insecticide DDT has a half-life in the human body of approximately 7 years. That is, in 7 years its concentration. Although DDT is no longer in use in the United States. It was estimated that 25 years ago the average farm worker had a body DDT concentration of 22 ppm (parts per million by weight). Estimate what the farm worker's present concentration would be.