
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
The lengths of shadows from the sun starting from Winter Solstice form an arithmetic progression among the twelve solar terms. Given that the length of the shadow on the day of Spring Equinox is 10.5 feet and on the day of Start of Summer is 4.5 feet, find the length of the shadow on the day of Vernal Equinox.

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