Harry has 3 sisters and 5 brothers.  His sister Harriet has $\text{S}$ sisters and $\text{B}$ brothers.  What is the product of $\text{S}$ and $\text{B}$?
$\text{(A)}\ 8 \qquad \text{(B)}\ 10 \qquad \text{(C)}\ 12 \qquad \text{(D)}\ 15 \qquad \text{(E)}\ 18$
Harry has 3 sisters and 5 brothers. His sister, being a girl, would have 1 less sister and 1 more brother.
$S = 3-1=2$
$B = 5+1=6$
$S\cdot B = 2\times6=12=\boxed{C}$