
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 order to enrich students' extracurricular activities, a certain school launched a "Nest Reading Month" activity and purchased two types of books, $A$ and $B$, as prizes. It is known that the unit price of type $A$ books is $2.5$ times the unit price of type $B$ books, and the quantity of type $A$ books purchased separately with $700$ yuan is $21$ less than the quantity of type $B$ books purchased separately. What are the unit prices of type $A$ and type $B$ books?

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