The Decay Constant of a Radioactive Nuclide Is $3.1 \times 10 ^ { - 3 } \mathrm {~s} ^ { - 1 }$

Multiple Choice

The decay constant of a radioactive nuclide is $3.1 \times 10 ^ { - 3 } \mathrm {~s} ^ { - 1 }$ . At a given instant, the activity of a specimen of the nuclide is $70 \mathrm { kBq }$ . How much later has the activity declined to $10 \mathrm { kBq }$ ?

A) $880 \mathrm {~s}$
B) $690 \mathrm {~s}$
C) $630 \mathrm {~s}$
D) $750 \mathrm {~s}$
E) $820 \mathrm {~s}$