
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 angle between vectors $\overrightarrow{a}$ and $\overrightarrow{b}$ is $\dfrac {2π}{3}$, $|\overrightarrow{a}|=2$, $|\overrightarrow{b}|=3$, let $\overrightarrow{m}=3 \overrightarrow{a}-2 \overrightarrow{b}$, $\overrightarrow{n}=2 \overrightarrow{a}+k \overrightarrow{b}$
(I) If $\overrightarrow{m} \perp \overrightarrow{n}$, find the value of the real number $k$;
(II) When $k=- \dfrac {4}{3}$, find the angle $θ$ between vectors $\overrightarrow{m}$ and $\overrightarrow{n}$.

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