Choose the 1st letter 24 ways. Not I or O Choose the 2nd letter 23 ways. Not I or O or the 1st letter. Choose the 3rd letter 23 ways. Not I or O or the 2nd letter. Choose the 4th letter 23 ways. Not I or O or the 3rd letter. Choose the 5th letter 23 ways. Not I or O or the 4th letter. Choose the 6th letter 23 ways. Not I or O or the 5th letter. Choose the 1st digit 9 ways. Not 0 Choose the 2nd digit 9 ways. Can be 0 but not the 1st digit. Choose the 3rd digit 8 ways. Can be 0 but neither the 1st nor the 2nd digit.Edwin