All you need to find is a nine-digit number that has the following properties:
It contains all the digits from one through to nine.
If you round the units the number increases in value. Then if you round the tens the number decreases in value. And this pattern continues for eight roundings.
The result after eight roundings is 500000000.
After four roundings the sum of the digits is 24.
Answer at 9.00 on Monday