
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
To pay for the shipping of four parcels, 4 different postage stamps with a total value of 84 kopecks were needed. Determine the cost of the stamps purchased by the sender, given that the values of these stamps form an arithmetic progression, and the most expensive stamp is 2.5 times more expensive than the cheapest one.

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