
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 that ${b_n}$ is a positive geometric sequence, $b_2=2$, $b_4=8$, and the sequence ${a_n}$ satisfies: $a_n b_n - 1 = \log_2 b_n$.
(I) Find the general terms for the sequences ${a_n}$ and ${b_n}$;
(II) Find the sum of the first $n$ terms of the sequence ${a_n}$, denoted as $T_n$, and find the range of $\lambda$ such that $(-1)^n \lambda < T_n$ always holds.

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