Until the OA is posted, this answer will be based on my own understanding, therefore susceptible to be incorrect.
The wording of this problem seems off to me. Anyway, let's solve this.
First of all, we need to understand and rephrase the problem.
We are told that the advetising rate "a" is inversely proportional to the productivity measure "b". Algebraically it means that there's a constant C such as : \(a=\frac{C}{b}\) (1)
Likewise, we are told that the productivity measure "b" is inversely proportional to the labor cost "c". Algebraically it means that there's a constant D such as : \(b = \frac{D}{c}\) (2)
So we're told that to see whether the labor cost is at least 200 when the productivity measure is at least 100.
Meaning that we need to find the value of the constant D.
Statement 1 : when\(c >=100\) then \(b >=50\)
Using equation (2), we get : \(D = b*c\) which means that given the statement, \(D >= 5000\).
If we consider the lowest possible value of D, i.e 5000, we get for \(b >= 100\), \(\frac{D}{c} >= 100\), meaning that \(\frac{5000}{c} >=100\), therefore
\(c <= 50\).
Which means that the labor cost will be at most 50 when the productivity measure is at least 100 given \(D = 5000\).
In fact the more D increases, the more c decreases. So statement 1 is sufficient.
Statement 2 : when \(c = 100\) then \(a = 100\)
Since a and c are not directly linked, then using both equations 1 & 2, we can find the link between the two variables :
We have : \(a=\frac{C}{b}\)
and \(b = \frac{D}{c}\)
Therefore, by putting b's expression in a, we get \(a = c*\frac{C}{D}\)
Since a = c, then we get C = D. And since there's no further information to be gained from this statement (remember that we're looking for D's value), then this statement is insufficient.
The final answer is A.Hope that helped