A can do a piece of work alone in 15 days, while B complete the same piece of work alone in 12 days. If they work on it together for 5 days, then the fraction of the work that will be left is:
\( \frac{3}{4} \)
\( \frac{5}{8} \)
\( \frac{1}{4} \)
\( \frac{5}{7} \)
A sum invested at a certain rate of interest per annum, compounded annually, amounts to ₹14,400 in 2 years and to ₹25,920 in 4 years. What is the sum invested?