Phosphorus-32, A $\beta$ -Emitter, Is a Radioactive Isotope Used in Many Biomedical Applications

Phosphorus-32, a $\beta$ -emitter, is a radioactive isotope used in many biomedical applications.How much time has passed if the ratio of 32S to 32P is 4 to 5?( The half-life of phosphorus-32 is 14.3 days.)

A) 11.4 days
B) 16.7 days
C) 4.60 days
D) 12.1 days
E) 16.9 days