Verified answer

m₀ = 10⁻²⁴ г

N = 89*10²³

V = 1 см₃

ρ = m / V = m₀ * N / V

ρ = 10⁻²⁴ г * 89*10²³ / 1 см³ = 8,9 г/см³ = 8900 кг/м³