
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
In their base $10$ representations, the integer $a$ consists of a sequence of $1000$ sixes and the integer $b$ consists of a sequence of $1000$ sevens. What is the sum of the digits of the base $10$ representation of $9ab$?
A) 18876
B) 19986
C) 20000
D) 21000

Present the answer in LaTex format: \boxed{Your answer}
user