An octal (base 8) number is a number whose digits can be any of the numbers 0 through 7. In each case, determine how many 4-digit octal numbers are possible.
If the first digit can be 0, we have 8 possibilities for each place....
So 8^4 = 4096 numbers
If the first digit can't be 0, we have 7 ways to fill the first position and 8 ways for the other three positions.
7 * 8^3 = 3584 numbers
