In a radioactive sample, ⁴⁰₁₉K nuclei either decay into stable ⁴⁰₂₀Ca nuclei with decay constant 4.5 × 10⁻¹⁰ per year or into stable ⁴⁰₁₈Ar nuclei with decay constant 0.5 × 10⁻¹⁰ per year. Given that in this sample all the stable ⁴⁰₂₀Ca and ⁴⁰₁₈Ar nuclei are produced by the ⁴⁰₁₉K nuclei only. In time t × 10⁹ years, if the ratio of the sum of stable ⁴⁰₂₀Ca and ⁴⁰₁₈Ar nuclei to the radioactive ⁴⁰₁₉K nuclei is 99, the value of t will be, [Given: ln 10 = 2.3]