A, b, and c are used as variables.. letters in the place of the where a number would originally be. So in that statement, a is less then b while b is less then c making c the largest number, the one greater upon the three.
I think is the first one because is either heads or tail, so is a 50-50 chance, so they are equally probability to be either one...
So, 0.5^5 is 0.03125
multiply that by 125 and get your answer.
*3.90625* (4)
just saying, I got the 0.5^5 thing because 5 is the number of half-lives (x) and 0.5 is the rate of loss (or whatever its called).
If it were to gain, you would put 1.5
The answer 101. 99+100+101+102+103 = 505