A XXXXXXXXXXmL sample water of unknown source was diluted to XXXXXXXXXXmL total volume. A 50.00 mL aliquot of this stock solution was titrated with XXXXXXXXXXM EDTA solution. The hardness of the water...

A 100.00 mL sample water of unknown source was diluted to 250.00 mL total volume. A 50.00 mL aliquot of this stock solution was titrated with 0.004000 M EDTA solution. The hardness of the water in ppm (mg/L) CaCO3 (MM = 100.09) in the original sample is 321.0 ppm. What is the volume (in mL) of EDTA used?