
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
A tangent line l is drawn from point M(0, 2) on the circle C: (x-4)^2 + (y+1)^2 = 25, and it is parallel to the line l′: 4x-ay+2=0. Find the distance between lines l′ and l.

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