A student prepared four standard solutions of (NH4)2Fe(SO4)2 and measured their absorbance at 505 nm. She created a calibration plot with the best-fit line of y =
9372 x + 0.0539. She measured the absorbance of her diluted unknown sample
solution as (8.69x10^-1) nm.
If she prepared her diluted sample solution by diluting 10.00 mL of the original
solution to a total volume of 50.00 mL with deionized water, what is the
concentration of Fe2+ in her original solution?