A calibration curve for the colorimetric determination of phosphorous in urine is prepared by reacting standard solutions of phosphate with molybdenum (VI) and reducing the phosphor-molybdic acid complex to produce the characteristic blue color. The measured absorbance A is plotted against the concentration of phosphorous. From the following data, determine the linear least-squares line and calculate the phosphorous concentration in the urine sample:

ppm P 1.00 2.00 3.00 4.00 Urine sample A 0.205 0.410 0.615 0.820 tel 0.625