  
 Exa -12.5(a)   
The decay constant is 2.970679e-006
 /sec 
 Exa -12.5(b)   
The decay constant is equal to probability of decay in one second hence 2.970679e-006 
 
 Exa -12.5(c)   
The activity was found out to be 9.036566e+009 Ci 
 Exa -12.5(d)   
The activity after one week was found out to be 1.50e+009 decays/sec 