Answer
Sample with 20 ppb lead concentration is higher than the acceptable limit.
Sample with 0.0030 ppm lead concentration is lower than the acceptable limit.
Work Step by Step
20. ppb=$ \frac{20\,\mu g}{kg}=\frac{20\,\mu g}{L}$
(as 1 kg water has volume 1 L)
$=\frac{0.020\,mg}{L}$
This concentration is higher than the acceptable limit. (Acceptable limit=0.015 mg/L)
0.0030 ppm=$\frac{0.0030\,mg}{kg}=\frac{0.0030\,mg}{L}$
This concentration is lower than the acceptable limit.
