Answer
$C=4$
Work Step by Step
The variation model described by the problem is $
C=\dfrac{k}{D}
.$
Substituting the known values in the variation model above results to
\begin{array}{l}\require{cancel}
12=\dfrac{k}{8}
\\
12(8)=k
\\
k=96
.\end{array}
Therefore, the variation equation is
\begin{array}{l}\require{cancel}
C=\dfrac{96}{D}
.\end{array}
Using the variation equation above, then
\begin{array}{l}\require{cancel}
C=\dfrac{96}{24}
\\
C=4
.\end{array}
