Adrian read about a new antimicrobial in a popular magazine. The advertisement claimed that the product Bactokil prevents bacterial growth. So, Adrian conducted a controlled experiment to test the product claims. Adrian added 1 mL of a solution containing different concentrations of Bactokil to equivalent samples of Escherichia coli bacteria and plated them in Petri dishes. After 24 hours, he counted the number of colonies on each plate. A graph of his results is shown below.