Question: 2015 Fall Midterm - 3
Let $A$ be a set of 6 elements and let $B$ be a set of 13 elements. How many one-to-one (i.e.,
injective) functions $f : A \rightarrow B$ are there?
(a)
$8 \cdot 9 \cdot 10 \cdot 11 \cdot 12 \cdot 13$
(b)
$6 \cdot 7 \cdot 8 \cdot 9 \cdot 10 \cdot 11 \cdot 12 \cdot 13$
(c)
$7 \cdot 8 \cdot 9 \cdot 10 \cdot 11 \cdot 12 \cdot 13$
(d)
$5 \cdot 6 \cdot 7 \cdot 8 \cdot 9 \cdot 10 \cdot 11 \cdot 12 \cdot 13$