145. Solving a chemistry problem

59. For an oil sample, standard and analyzed, weighing 1.0000 g each, was diluted 10 times with methyl isobutyl ketone and sprayed in a flame of an atomic adsorption spectrophotometer. The optical density of the vanadium line for a sample with a known vanadium content of 0.01% was Ast = 0.740 and for a sample with an unknown content of Ax = 0.520.