One is B, two is C, and I'm not sure but I think three is A or C.
Set this up as
10 = 40 (1/2)t/28
and solve for t in years.
10/40 = (1/2)t/28
log(0.25) = (t/28) log(0.5)
t = 28 log(0.25) / log(0.5) years = 56 years
Test the answer:
56 years = 2(28 years) = 2 half-lives, so the remaining amount should be 1/2 of 1/2 of the initial amount, i.e. 1/4 of the initial amount, and 10 mg = 1/4 of 40 mg.
Spain, Italy, Portugal, Andorra, and Greece are in Southern Europe. Greece follows the <span>Greek Orthodox, while Spain, Italy, Portugal, and Andorra are Roman Catholic.</span>
<span>In the flattened disk</span>
