:Answer 
1.0/5 
7 
 
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For this problem, we use the formula for radioactive decay which is expressed as follows: 
 
An = Aoe^-kt 
 
where An is the amount left after time t, Ao is the initial amount and k is a constant. 
 
We calculate as follows: 
 
at hal-life equal to 5700, 
 
An = Aoe^-kt 
0.5 = e^-k(5700) 
k = 1.22x10^-4 
 
An = A