
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
Given line $l_1$: $x - 2y - 1 = 0$, and line $l_2$: $ax - by + 1 = 0$, where $a, b \in \{1, 2, 3, 4, 5, 6\}$, determine the probability that the intersection point of lines $l_1$ and $l_2$ is located in the first quadrant.

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