Let $\displaystyle {S}$ be the universal set, where:
$\displaystyle {S}={\left\lbrace{1},{2},{3},\ldots,{23},{24},{25}\right\rbrace}$
Let sets $\displaystyle {A}$ and $\displaystyle {B}$ be subsets of $\displaystyle {S}$, where:

Set $\displaystyle {A}={\left\lbrace{1},{1},{3},{11},{15},{17},{18},{21},{23}\right\rbrace}$

Set $\displaystyle {B}={\left\lbrace{1},{4},{6},{8},{11},{12},{14},{15},{17},{20},{23},{25}\right\rbrace}$

Set $\displaystyle {C}={\left\lbrace{2},{9},{10},{14},{21},{23},{25}\right\rbrace}$

Find the number of elements in the set $\displaystyle {\left({A}\cap{C}\right)}\cap{B}^{{c}}$
$\displaystyle {n}{\left[{\left({A}\cap{C}\right)}\cap{B}^{{c}}\right]}$ =

You may want to draw a Venn Diagram to help answer this question.