
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 unit organized its staff to visit the Shanghai World Expo through a travel agency. Here is a conversation about the charging standards between the team leader and the travel agency guide:

Team Leader: What is the per-person charge?

Guide: If the number of people does not exceed 30, the per-person travel cost is 120 yuan.

Team Leader: How about a discount for more than 30 people?

Guide: If it exceeds 30 people, for every additional person, the per-person travel cost will decrease by 2 yuan, but the per-person travel cost shall not be lower than 90 yuan.

After visiting the World Expo according to the travel agency's charging standards, the unit paid a total of 4000 yuan to the travel agency. Based on the information above, how many people did the unit have for this visit to the World Expo?

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