What is the percent by m of calcium carbonate in eggshell?

react 3.953 g of egg shell with 50 cm^3 of 1 mol dm^-3 hydrochloric acid. after shell reacted, solution was placed in flask, and volume made up 100 cm^3. 10 cm^3 reacted exactly with 12.65cm^3 of .100 mol dmcm^-3 NoOH.