How many different sequences of 4 digits are possible if the first digit must be 3, 4, or 5 and if the

sequence may not end in 000? Repetition of digits is allowed.

Number of choices for the first digit:3

Number of choices for the second digit:10
ditto for third digit: 10
ditto for the fourth digit: 10
Calculate the total number of possibilities, less 3 (that is 3000,4000,5000).