Questions: A researcher for the EPA measured the amount of arsenic in the water near a sewage treatment plant. Over 12 days, he took n=40 measurements (in ppb). His sample data is summarized in the frequency distribution polygon shown below. How many measurements taken in this time frame were within [65,70) ppb?

Transcript text: A researcher for the EPA measured the amount of arsenic in the water near a sewage treatment plant. Over 12 days, he took $n=40$ measurements (in ppb ). His sample data is summarized in the frequency distribution polygon shown below. How many measurements taken in this time frame were within $[65,70)$ ppb?