#### Answer

Fill the blanks with
... factorial ...
... 5 ... 1 ...
... 1 ...

#### Work Step by Step

See: Factorial Notation, page 696.
$n!=n(n-1)(n-2)\cdots(3)(2)(1)$
and
$0!=1$
------------------
5! called "5 factorial"....
product of... integers from 5 down through 1.
By definition, $0!=1$.