If today is Friday, what's the day of the ninth power after the ninth power from today?

If today is Friday, what's the day of the ninth power after the ninth power from today?

The 9th power of 9
The ninth power of 9 is 387420489
What is the ninth power of 387420489
Then subtract 2 (Saturday, Sunday)
Except on 7 (1 week, 7 days)
If not, it's Sunday
If there is a remainder, the remainder is the day of the week
(for example, the remainder is 3, Wednesday)
Because a set of rules is Monday to 7, minus Saturday and Sunday
After that, a new set of rules will be opened, and the quotient removed is the number of rules experienced
The remainder is the number that is not enough to form a new set of laws after so many sets of laws,
So the rest is the day of the week
For example, the remaining 3
One set of rules is 7
Only three
Monday, Tuesday and Wednesday (3)
The last one is the day of the week
What grade is this?