The count rate from a radioactive specimen was recorded as follows:
Time t (s): 0, 10, 20, 30
Count rate (cps): 8000, 5940, 4410, 3280
Assuming the count rate is proportional to the number of undecayed nuclei, estimate the decay constant λ of the isotope.
a) 0.015s−1
b) 0.026s−1
c) 0.030s−1
d) 0.069s−1