
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 ferry boat starts shuttling people to a festival on an island at 9 AM and makes its last trip at 4 PM. The trips occur every half hour. On the first trip at 9 AM, there were 120 people, and on each subsequent trip, the number of people decreased by 2 from the previous trip. How many people were ferried to the island in total that day?
A) 1500
B) 1590
C) 1605
D) 1620

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