3) Californium-252 has a half-life of 2.645 years. If the equation describing the decay of the readioactive nuclei is given by $\displaystyle y=y_0e^{kt}$, find:

a) the value of k

b) how long it will take for 95% of the radioactive nuclei to disintegrate.

Please offer a step-by-step solution; I don't know how to do half-lifes really, but need to for my exam.