Eight children — A, B, C, D, E, F, G, and H — are going to sit in eight chairs in a row. Child C must be somewhere to the left of child D. How many possible configurations are there for the children? Choose the correct choice from the following answers:
A) 2520  B) 5040  C) 10,080  D) 20,160  E) 40,320
The number of ways to seat 8 people is 8! = 40,320.   Child C will sit to the left of Child D in exactly half of these arrangements.   The total number of possible arrangements is 40,320/2 = 20,160   The answer is 20,160.
<result>D</result>
Eight children — A, B, C, D, E, F, G, and H — are going to sit in eight chairs in a row. Child C must be somewhere to the left of child D. How many possible configurations are there for the children?