Answer:
The third and the fourth option.
![3Mg+1Fe_2O_3 \\ = 3MgO + 2Fe[tex]3Mg+1Fe_2O_3 \\ = 3MgO + 2Fe \\](https://tex.z-dn.net/?f=3Mg%2B1Fe_2O_3%20%5C%5C%20%20%3D%203MgO%20%2B%202Fe%3C%2Fstrong%3E%3C%2Fp%3E%3Cp%3E%3Cstrong%3E%5Btex%5D3Mg%2B1Fe_2O_3%20%5C%5C%20%20%3D%203MgO%20%2B%202Fe%20%5C%5C%20)

Explanation:
The number of products and reactants are balanced
Well, . .
Let's divide the gallon into 4 Quarts.
if 1 part cleaner need to be mixed every 3 parts of water, it's means that you need about 1/4 gallon of cleaning solution
hope this helps