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7.- The counting speed in a radioactive sample is 8,000 counts / s at the moment...

7.- The counting speed in a radioactive sample is 8,000 counts / s at the moment
t = 0 s. After 10 minutes only 1,000 accounts / s are detected.
a. What is the half-life?
b. What is the decay constant?
c. What counting speed will be detected after one minute?

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