Calcium in a sample solution is determined by atomic absorption spectrophotometry. A stock solution of calcium is prepared by dissolving 1.834g CaCl 2 ．2H 2 O in waterand diluting to 1L. This is diluted 1:10. Working standards are prepared by diluting thesecond solution，respectively，1:20，1:10，and 1:5. The sample is diluted 1:25. Strontium chloride is added to all solution before dilution，sufficient to give 1%(wt/vol) to avoidphosphate interference. A blank is prepared，to give 1% SrCl 2 . Absorbance signals, when thesolution are aspirated into an air-acetylene flame, are as follows: blank, 0.015; standards,0.106, 0.201, and 0.385; sample, 0.296. What is the concentration of calcium in the samplein mg/L?