Calculate the Ksp for calcium sulfate if its solubility is 0

Calculate the Ksp for calcium sulfate if its solubility is 0.67 g/L

First change 0.67g/L into molarity

(0.67g/L)(1mol/136.15g)= 4.9e-3 M

Then write a chemical equation for the dissolution of CaSO4

CaSO4 <--> Ca2+ + SO4 2-

setting up an equilibrium expression gives us
[Ca2+][SO4 2-] = ksp
since the concentrations of Ca and SO4 are the same, we end up with

(4.9e-3)^2 = 2.4e-5

so the ksp of CaSO4 is 2.4e-5