Does anyone have a formula for this problem?

V Serial numbers for a product are to be made using 3 letters followed by 3 digits. The letters are to be taken from the rst 5 letters of the alphabet, with no repeats. The digits are taken from the 10 digits (0, 1, 2, ..., 9), with no repeats. How man!r serial numbers can be generated? (If necessary, consult a list of formulas.)