Which Calculation Was Done to Determine the Rate of Calcite

Which calculation was done to determine the rate of calcite accumulation in soils in Gile and Grossman's experiment?

A) the number of kilograms of calcite found in the soil column divided by time (calculated by radioactive carbon dating)
B) the number of kilograms of calcite found in the soil column (estimated by comparison with known sources) multiplied by time (estimated by comparison with similar rock layers elsewhere)
C) time (calculated by radioactive carbon dating) divided by the number of kilograms of calcite found in the soil column (measured in the lab)
D) time (calculated by using known fossils) divided by the number of kilograms of calcite found in the soil column