A compound X is to be determined by UV-visible spectrophotometry. A calibration curve is constructed from standard solutions of X with the following. results: 0.50 ppm, A = 0.24; 1.5 ppm, A = 0.36; 2.5 ppm, A = 0.44; 3.5 ppm, A = 0.59; 4.5 ppm, A = 0.70. A solution of unknown X concentration had an absorbance of A = 0.50. Find the slope and intercept of the calibration curve, the standard error in Y, the concentration of the solution of unknown X concentration, and the standard deviation in the concentration of X. Construct a plot of the calibration curve and determine the unknown concentration by hand from the plot. Compare it to that obtained from the regression line.