More conversions

[BYRPV@ccmail.ceco.com]

 Here's another easy one:
 
 Sb-125 is a fission with a relatively short half life which may be used by 
 someone to tell how fresh a batch of fission products is.
 
 How many atoms of the isotope Sb-125 are in one uBq?  Compare this to the 
 atoms in a cubic meter of air at one DAC (class D) of the same.
 
 Second, why in the world would anyone care to measure a quantity such as 
 the uBq in a cubic meter of air?
 
 Paul Vitalis
 byrpv@ccmail.ceco.com