A spectrophotometric method for the quantitative determination of Pb 2+ levels in blood gives a linear normal calibration curve for which S stand =...

A spectrophotometric method for the quantitative determination of Pb2+ levels in blood gives a linear normal calibration curve for which Sstand = (0.296 μg -1L)CS + 0.003. What is the Pb2+ level (in ppb) in a sample of blood if Ssample is 0.397?

Answer is 1.33 ug/L