Answer: Option A
$$\eqalign{
& {\text{According to the question,}} \cr
& {\text{Principal}} = {\text{Rs}}{\text{. }}2100 \cr
& {\text{Amount}} = {\text{Rs}}{\text{. }}2352 \cr
& {\text{SI}} = {\text{A}} - {\text{P}} \cr
& \,\,\,\,\,\,\, = 2352 - 2100 \cr
& \,\,\,\,\,\,\, = {\text{Rs}}{\text{. }}252 \cr
& {\text{Time = 2 years,}} \cr
& {\text{Let rate = R% }} \cr
& {\text{R = }}\frac{{252}}{{2100}} \times \frac{{100}}{2}{\text{ = 6% }} \cr
& {\text{New rate of interest}} \cr
& {\text{ = (6}} - {\text{1)}} \cr
& {\text{ = 5% }} \cr
& {\text{New interest}} \cr
& {\text{ = }}\frac{{2100 \times 5 \times 2}}{{100}} \cr
& {\text{ = Rs}}{\text{. 210}} \cr
& {\text{Hence required interest}} \cr
& {\text{ = Rs}}{\text{. 210}} \cr} $$