I do not need exact answers with numbers just explanations of how to do it would be fine, thank you.

Radioactive copper – 64 decays with a half life of 12.8 days

a. What is the value of k in s-1

b. A sample contains 28. mg of copper 64. How many decay events will be produced in the fist second.

Assume the mass of 64g

c. A chemist obtains a fresh sample of copper 64 and measuress radioactivity. She then determines that to do an experiment the radioactivity cannot fall below 25% of the intial measured value

How long does she have to do an experiment

Just please tell me what to do I’m completely lost and cannot find how to do it in the book

Thank you