OK,I take this risk. But i really do not want to get a warning.
Did you remember i told you better use the equilibrium :
Ca2+ + SO42-
CaSO4
The concentration of Ca and SO4 ionized from CaSO4 is always the same,(remember this).
when you add SO4 the equilibrium will go right,the concentration of Ca and SO4 will both decrease,but the [SO42-] is different from [Ca2+](based on the Le Chatelier principle).
Let's do it! Step by step.
first,you can calculate the final [Ca2+]=2.73mol/0.239L * 0.1%
Then you can calculate the [SO42-] by using the Ksp
KspCaSO4=[Ca2+][SO42-]=6.1x10^-5
substituting the final [Ca2+] to Ksp equilibrium you can get the [SO42-] in the solution,
but don't forget the SO42- in CaSO4 ,which is also from Na2SO4 you add.
[SO42-] in the solution=KspCaSO4/final [Ca2+]
Total nSO42- =[SO42-] in the solution*V + nSO42- in CaSO4
can you follow the above to get the right answer?