I need help with a and b. Thank you!

Imagine fresh water containing 0.02MCa2+ and 0.02MSO42 fills an evaporite basin lined with gypsum. Assume that the water is at 25C, under 1atm of pressure, and that Mg2+ and SO42 are the only major dissolved ions. For reference, the thermodynamic equilibrium constant for gypsum ( CaSO42H2O(5)) dissolution at standard conditions is 2.4105mol2L2. The reaction is: CaSO42H2O(5)>Ca2+(20)+SO4(3(2)+2H2O(1) a. Write the equilibrium constant expression describing the concentration of dissolved ions in this system with respect to the equilibrium constant (in this case, the equilibrium constant is referred to as a solubility product). b. Given the conditions above, what is the value of ion activity product (IAP) in this system? Note that since this solution has a low ionic strength, ion pairing is negligible and activity coefficients () are 1