
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
An electrician was called to repair a string of four serially connected light bulbs, one of which burnt out. It takes 10 seconds to unscrew any bulb from the string and 10 seconds to screw one in. The time spent on other actions is negligible. What is the minimum amount of time the electrician needs to find the burnt-out bulb, if he has one spare bulb?

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