first letter must be a C
that is 1 choice, first slot is 1 choice
3 letter spaces left
we ar allowed to repeat
ther are 26 letters in the alphabet
and 10 digits
so there are 26 choices for each of the 3 letter slots and 10 choices for the last 2 slots
so the number of licence plates is 1*26*26*26*10*10=1757600 different licecne plates