Question: 2015 Winter Midterm - 3
Let $A$ be a set of 7 elements and let $B$ be a set of 15 elements. How many one-to-one (i.e.,
injective) functions $f : A \rightarrow B$ are there?
(a)
$9 \cdot 10 \cdot 11 \cdot 12 \cdot 13 \cdot 14$
(b)
$8 \cdot 9 \cdot 10 \cdot 11 \cdot 12 \cdot 13 \cdot 14 \cdot 15$
(c)
$9 \cdot 10 \cdot 11 \cdot 12 \cdot 13 \cdot 14 \cdot 15$
(d)
$10 \cdot 11 \cdot 12 \cdot 13 \cdot 14 \cdot 15$