Explanation:

- Step 1: Determine the principal (P) from compound interest.

- Compound interest formula: $A=P\times (1+r{)}^n$.

- Given: $A=3456$, $r=20\mathrm{\%}=0.2$, $n=3$.

- $3456=P\times (1.2{)}^3$.

- $3456=P\times 1.728$.

- $P=\frac{3456}{1.728}=2000$.

- Step 2: Calculate simple interest for $3P$.

- $3P=6000$.

- Simple Interest formula: $SI=P\times r\times t$.

- Given: $r=15\mathrm{\%}=0.15$, $t=12$.

- $SI=6000\times 0.15\times 12=10800$.

- Correct Answer:

- The interest received is Rs. 10800.

- ?? Option 1: Rs. 10800 is the correct choice.