The Kingdom of Chemithia- Part 1

Far away, nestled in a lush green valley, is the kingdom of Chemithia. The residents of Chemithia love to do chemistry, and the most skilled chemists are taken in to work in King Antimony's court. However, there is a rigorous test that all Chemithian residents need to pass if they wish to work in the court. Your name is Aurous Promethian, and your lifelong dream has been to work as a chemist in King Antimony's court. You go to write the test along with most of the other residents of Chemithia. As you begin writing, you need to solve the following question:

In order to soften the water coming from the Lanthanus River, we need to remove the ions of $Mg^{2+}$ and $Ca^{2+}$ present in it. Our water has 48 ppm of $Mg^{2+}$ ions and 40 ppm of $Ca^{2+}$ ions. For this, we use Sodium Tripolyphosphate (STPP). This compound has the formula $Na_5P_3O_{10}$ . The following reactions take place when Sodium Tripolyphosphate (STPP) is added to water: - $Na_5P_3O_{10}$ + $Mg^{2+}$ ----> $Na_3MgP_3O_{10}$ + $2Na^{+}$

$Na_3MgP_3O_{10}$ + $Ca^{2+}$ ----> $NaCaMgP_3O_{10}$ + $2Na^{+}$

If the king needs 10 litres of softened water for hosting his guests, which of the following are true about the water treatment?

(1) In order to fully remove the $Mg^{2+}$ ions, we need at least 7.36 grams of STPP.

(2) In order to fully soften the water by removing all $Mg^{2+}$ and $Ca^{2+}$ ions, we need at least 11.04 grams of STPP.

(3) In order to fully soften the water by removing all $Mg^{2+}$ and $Ca^{2+}$ ions, we need at least 7.36 grams of STPP.

(4) In order to remove all $Mg^{2+}$ ions, we need at least 3.68 grams of STPP.

What is the sum of the correct options? (Eg. If the answer is 3 and 4, input 7 as your answer)

This question is part of my set Tales of Chemithia ! Give it a try; it's a story woven together by Chemistry problems!