a) Rs. 210
b) Rs. 220
c) Rs. 242
d) Rs. 252

Answer: a
Explanation:
$$\eqalign{ & {\text{Principal}} = {\text{Rs}}{\text{. }}2100 \cr & {\text{Amount}} = {\text{Rs}}{\text{. }}2352 \cr & {\text{SI}} = {\text{A}} – {\text{P}} \cr & \,\,\,\,\,\,\, = 2352 – 2100 \cr & \,\,\,\,\,\,\, = {\text{Rs}}{\text{. }}252 \cr & {\text{Time = 2 years,}} \cr & {\text{Let rate = R% }} \cr & {\text{R = }}\frac{{252}}{{2100}} \times \frac{{100}}{2}{\text{ = 6% }} \cr & {\text{New rate of interest}} \cr & {\text{ = (6}} – {\text{1)}} \cr & {\text{ = 5% }} \cr & {\text{New interest}} \cr & {\text{ = }}\frac{{2100 \times 5 \times 2}}{{100}} \cr & {\text{ = Rs}}{\text{. 210}} \cr & {\text{Required interest}} \cr & {\text{ = Rs}}{\text{. 210}} \cr} $$