In one experiment, a student added a total of 15.00 mL of 0.5241 M HCl to 1.4881 g to of an unknown which contained CaCO3 (molar mass = 100.09 g/mol). The resulting solution required 12.21 mL of 0.1211 M NaOH to back titrate the excess HCl. What was the percent CaCO3 in the unknown? Report your answer to two (2) decimal places.