143. Determine the mass fraction (%) of copper in aluminum, if the following results were obtained during photometry using the method of three standards:
Parameter Reference Analyzed sample
1 2 3
ω(Cu), % 0.25 0.80 1.20 ?
S(Cu) 0.25 0.54 0.61 0.40
S(Al) 0.42 0.44 0.41 0.46

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