I am sure there must be a formula to calculate water volume based on salinity. Here is my example:

Example 1:

If a pond has 0.00% salinity and you add one 25kg bag of salt and the salinity goes up to 0.32%, what is the volume of the water?

Example 2:

If a pond has 0.13% salinity and you add 4 x 25kg bags of salt and the salinity goes up to 0.42%, what is the volume of the water?

Does anybody have such a formula where you can add in the start salinity, the end salinity and the kg of salt and then it calculates the pond volume?