Employees of a certain company are each to receive a unique 10-digit identification code consisting of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 such that no digit is used more than once in any given code. In valid codes, the second digit in the code is exactly twice the first digit. How many valid codes are there?  Choose the correct choice:
A) 145,660
B) 149,720
C) 155,420
D) 161,280
E) 167,480
There are 8! ways to make codes starting with 12.   There are 8! ways to make codes starting with 24.   There are 8! ways to make codes starting with 36.   There are 8! ways to make codes starting with 48.   The number of codes is 4*8! = 161,280.   The answer is 161,280.
<result>D</result>
Employees of a certain company are each to receive a unique 10-digit identification code consisting of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 such that no digit is used more than once in any given code. In valid codes, the second digit in the code is exactly twice the first digit. How many valid codes are there?