Analytical Chem HELP PLEASE!

Hi! Any help would be greatly appreciated!

A spectrophotometric method for the analysis of iron has a linear calibration curve for standards of 0.00, 5.00, 10.00, 15.00, and 20.00 ppm. An iron ore sample with an expected iron content of 40 - 60% w/w is to be analyzed by this method. An approximately, 0.5 g sample is taken, dissolved in HCL, and diluted to 1 L in a volumetric flask with distilled water. A 5.00 mL aliquot is removed with a pipet. To what volume should it be diluted to minimize the uncertainty in the analysis??

I already know the answer is 100 mL but I'm unsure of how to get that. If you could just help me get started or tell me how to approach this problem, it would be greatly apprecitaed!

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