Concept:
When debentures are issued as collateral security:
No interest is paid on collateral debentures unless they are enforced.
Finance cost includes only interest on the actual loan.
Step 1: Interest on loan.
Loan amount:
\[
₹10{,}00{,}000
\]
Rate:
\[
12%
\]
\[
\text{Interest} = 10{,}00{,}000 \times 12% = ₹1{,}20{,}000
\]
Step 2: Debentures issued as collateral.
₹15,00,000 debentures are only a security.
No interest is paid unless default occurs.
Hence, ignore 8% debenture interest.
Final Answer:
\[
\boxed{\text{Finance Cost} = ₹1{,}20{,}000}
\]