Lead-196 has a half-life of 37 minutes it decays into thallium-196 suppose a sample contains 20 atoms of lead-196 and 60 atoms of thallium-196 about how old is the sample. A. 37 minutes
B. 111 minutes
C. 74 minutes
D. 148 minutes

for points guys

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.