3 × 104 J
5 × 104 J
6 × 104 J
7 × 104 J
E = ½nRT = ½PV = ½P(V) = ½P(m/ρ) = ½ * (8 × 104 N/m2) * (1 kg / 4 kg/m3) = 5 × 104 J