1. The approximate mass of air in the living room can be calculated using the formula: mass = density × volume. Air density is typically around 1.2 kg/m³. So, mass = 1.2 kg/m³ × (5.6 m × 3.6 m × 2.4 m). 2. Specific gravity is the ratio of the density of a substance to the density of a reference substance (usually water). In this case, specific gravity = density of granite / density of water. So, specific gravity = 2.8 g/cm³ / 1.0 g/cm³. 3. Average density of the Earth is calculated using the formula: density = mass / volume. The specific gravity is the ratio of Earth's average density to the density of water. Specific gravity = Earth's average density / density of water. Use the given mass (mE) and radius (RE) to find the volume of the Earth, then calculate density and specific gravity accordingly.