A 6.74 kg mixed-mineral sample contains chromite (FeCr2O4) as the only chromium-bearing ore. The sample is subjected to an industrial process, using a ferrosilicon alloy as a reducing agent, which quantitatively converts all of the chromium into 13.1 kg of a ferrochrome alloy (stainless steel) which is 13.4% Cr by mass. What is the percentage of chromite (FeCr2O4) in the original sample?