To determine the solubility of different salts in water we can use the solubility diagrams that have experimental data using different amounts of salt in 100 grams of water.
In the following figure I will make a diagram referring to those found in the literature. You can find these diagrams on the web looking for a solubility diagram of ...
At 100°C we will have a solubility of NaCl equal to 39.12g in 100 grams of water.
The density of water is 1g/mL, so,
100g of water = 100mL.
At 100°C we will have a solubility of NaCl equal to 39.12g in 100 mL of water.
So the answer will be 100°C