A small amount of $CaCO_3$ completely neutralized 525ml of N/10 HCl and no acid is left at the end.After converting all calcium chloride to $CaSO_4$,how much plaster of paris can be obtained?

Question

$(a)\;4.2g\qquad(b)\;2.1g\qquad(c)\;3.81g\qquad(d)\;4.38g$