
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
Let $e_1$ and $e_2$ be two unit vectors with an angle of $60^\circ$ between them. If $a = e_1 + \lambda e_2$ is perpendicular to $b = 2e_1 - 3e_2$, then find the value of $\lambda$.

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