Q$2.$ Explain whether each radiotracer listed below is good or bad for medical imaging. $($i$)(5$ pts$)$ E$=30$KeV $,$t $1/2=7$ hours; $($ii$)(5$ pts$)$ E$=150$ KeV $,$t $1/2=5$ hours; and $($iii$)$ E$=200$KeV $,$t $1/2=10$ days. $($iii$)(5$ pts$)$ The activity of an object at t$=0$ is $41010$ dps$.$ Its activity reduces to $11010$ dps after $5$ hours. Compute the expected number of radioatoms present at t$=0.$