During an experiment, a detector registers 1.20×106 disintegrations from a radioactive sample in the first 5.0 min and 0.70×106 disintegrations in the next 5.0 min. Assume the sample is not disturbed between the two counts.
(i) Calculate the decay constant λ of the nuclide.
(ii) Estimate the number of undecayed nuclei present at the start of the first counting interval.