80 kg of a radioactive material reduces to 10 kg in 1h. The decay constant of the material is

• A

  $5.80\times {10}^{-4} S^{-1}$

• B

  $1.16\times {10}^{-3} S^{-1}$

• C

  $2.32\times {10}^{-3} S^{-1}$

• D

  $4.64\times {10}^{-3} S^{-1}$