Radioactive Decay
A radioactive substance decays according to the formula Q(t) = Q0e^(-kt), where Q(t) denotes the amount of the substance present at time t (measured in years), Q0 denotes the amount of the substance present initially, and k (a positive constant) is the decay constant.
(a) Find the half-life of the substance in terms of k.
(b) Suppose a radioactive substance decays according to the formula Q(t) = 80e^(-0.0001231t). How long will it take (in years) for the substance to decay to half the original amount? (Round your answer to the nearest whole number.)