Of a certain sum, \[\frac{1}{3}rd\]is invested at 3%, \[\frac{1}{6}th\] at 6% and the rest at 8%. If the S.I. for 2 years from all these investments amounts to Rs.600, what was the original sum?

• A.  Rs.2000     
• B.      Rs.3000
• C.  Rs.4000     
• D.      Rs.5000