**A. RS. 3900**

B. RS. 3000

C. RS. 3281

D. RS. 3891

**Solution:**

Let the cost of a chair and that of a table be Rs. *x* and Rs. *y* respectively.

\[\left. \begin{array} { l } { \text { Then, } 10 x = 4 y \text { or } y = \frac { 5 } { 2 } x . } \\ { \therefore 15 x + 2 y = 4000 } \\ { \Rightarrow 15 x + 2 \times \frac { 5 } { 2 } x = 4000 } \\ { \Rightarrow 20 x = 4000 } \\ { \therefore x = 200 } \\ { \text { So, } y = ( \frac { 5 } { 2 } \times 200 ) = 500 } \\ { \text { Hence, the cost of } 12 \text { chairs and } 3 \text { tables :} }\\

{= 12 x + 3 y } \\ { \quad = \text { Rs. } ( 2400 + 1500 ) } \\ { \quad = \text { Rs. } 3900 } \end{array} \right.\]