
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 points A($x_1$, $y_1$) and B($x_2$, $y_2$), which are two distinct points on the ellipse C: $$\frac{x^2}{25} + \frac{y^2}{9} = 1$$, and point M(4, $\frac{9}{5}$). The distances from points A, M, and B to line l: $x = \frac{25}{4}$ form an arithmetic sequence.
(I) Find the value of $x_1 + x_2$;
(II) The perpendicular bisector of segment AB intersects the x-axis at point N. Find the equation of line MN.

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