请大家帮忙解答一道题，谢谢各位！

Q7:

A company has assigned a distinct 3-digit code number to each of its 330 employees.  Each code number was formed from the digits

2, 3, 4, 5, 6, 7, 8, 9

and no digit appears more than once in any one code number.  How many unassigned code numbers are there?

A.       6

B.       58

C.       174

D.      182

E.       399

答案是 A，请大家帮忙解答一下，多谢了

Select 3 out of 8 numbers. The total combinations are P(8,3)=8x7x6=336. Number of combinations not used = 336-330=6