A company plans to assign identification numbers to its employees

A company plans to assign identification numbers to its employees. Each number is to consist of four different digits from 0 to 9, inclusive, except that the first digit cannot be 0. How many different identification numbers are possible?

(A) 3,024 (B) 4,536
(C) 5,040
(D) 9,000
(E) 10,000

First digit can be chosen from 9 numbers (except 0) in 9C1 = 9 ways.

The rest of the 3 digits can be rearranged in 9P3 ways – 504.

Total number of identification numbers – 9 * 504

Ans B