
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 price level in the United States increased from 100 in 1939 to 500 forty years later in 1979. If the annual rate of price increase is the same every year, what is the annual percentage increase? (Note: $x < 0.1$, you can use: $\ln(1+x) \approx x$, and take $\lg 2 = 0.3$, $\ln 10 = 2.3$)

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