One of the main contaminants of a nuclear accident, such as that at Chernobyl, is strontium-90, which decays exponentially at a rate of approximately 2.4% per year. 

(a) Write the percent of strontium-90 remaining, P, as a function of years, t, since the nuclear accident.

(b) Graph P against t. 

(c) Estimate the half-life of strontium-90. 

(d) After the Chernobyl disaster, it was predicted that the region would not be safe for human habitation for 100 years. Estimate the percent of original strontium-90 remaining at this time.