
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 the sum of the first $n$ terms of the arithmetic sequence ${a_n}$ is $S_n$, and $a_2=8$, $S_4=40$. The sum of the first $n$ terms of the sequence ${b_n}$ is $T_n$, and $T_n-2b_n+3=0$, $n∈N^{*}$.
(I) Find the general term formula for the sequences ${a_n}$ and ${b_n}$;
(II) Let $c_n= \begin{cases} a_n, & \text{n is odd} \\ b_n, & \text{n is even} \end{cases}$, find the sum of the first $n$ terms of the sequence ${c_n}$, denoted as $P_n$.

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