**Category:** Inorganic Chemistry  
**Subtype:** Chemical Reactions, Stoichiometry  
**Problem Description:** This problem involves a mixture of metals (sodium, potassium, barium) and aluminum oxide reacting with water to produce hydrogen gas and a solution. The task is to determine the mass of a precipitate formed when hydrochloric acid is added to the resulting solution. 

**Key Points:**
- The total mass of the mixture is 46.6 grams.
- Oxygen constitutes 30.9% of the mixture's mass.
- The reaction with water produces 8.96 liters of hydrogen gas at standard conditions.
- The addition of 1.4 liters of 1 M HCl to the solution results in the formation of a precipitate, and the goal is to find the mass of this precipitate (m). 

**Options for m:** 
A. 23.4 g  
B. 27.3 g  
C. 31.2 g  
D. 15.6 g