
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
Points $R$ and $S$ are on line segment $CD$, with both points located on one side of the midpoint of $CD$. Point $R$ divides $CD$ in the ratio $1:4$, and point $S$ divides $CD$ in the ratio $1:2$. If the length of segment $RS$ is 3, then find the length of segment $CD$.
A) 15
B) 18
C) 21
D) 22.5
E) 24

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