
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
A company invests 720,000 yuan to build an environmentally friendly building materials factory. The operating costs in the first year are 120,000 yuan, and the operating costs increase by 40,000 yuan each year thereafter. The annual revenue from selling environmentally friendly building materials is 500,000 yuan. In which year will the factory's net profit reach its maximum?

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