The amount of a sample remaining after t days is given by the equation p (t) = a (1 / 2 )^ t / h, where a is the initial amount of the sample and h is the half-life, in days, of the substance. a sample contains 60% of its original amount of fermium-257. the half-life of fermium-257 is about 100 days. about how old is the sample?
a. 52 days
b. 60 days
c. 74 days
d. 136 days