find the greatest number

10,000  $\times$   10,000

use the given digits and form the greatest and the smallest 4 - digit number:

2 , 8 , 7 , 4

form the greatest 4 - digit number using the given digits :

5 , 4 , 0 , 3

form the smallest number using the given digits :

4 , 7 , 5 , 0