Strontium 90 is a radioactive material that decays according to the function Upper A left parenthesis t right parenthesis equals Upper A 0 e Superscript negative 0.0244 t Baseline comma

A(t)=A0e0.0244t, where Upper A 0

A0 is the initial amount present and A is the amount present at time t(in years). Assume that a scientist has a sample of 500

500 grams of strontium 90.

(a) What is the decay rate of strontium90?

(b) How much strontium 90 is left after 30

30 years?

(c) When will only 400

400 grams of strontium 90 beleft?

(d) What is thehalf-life of strontium90?