Help with python function.DO NOT USE LOOP (using unit testing)

****Note: cannot have a function that is built in or string manipulation

1) The first function is has a parameter of base eight that takes four digit number. The number that will return can be equivalent to base ten or in decimal. The answer is an integer (whole number). Number is 3562 (parameter is four digits and positive!) 1*8**3 + 1*8**2 + 1*8**1 + 1*8**0 (585) Must add and multiply digits, then create and return the resulting number in decimal