Question 1201686
.


The problem is posed/worded incorrectly.


OBVIOUSLY,  it assumes that there is some ordering of letters and digits,
like  " the letters go first "  or something of this kind.


It assumes,  but the given problem says nothing about this ordering.



Without such ordering,  the number of all possible plates is much greater.



And without such given info about ordering,  the solution should be different.