Consider the case of a bank with assets of $400 and liabilities of $300. Suppose the duration of the assets is 10 years, and the duration of the liabilities is 7 years. Also let the convexity of the assets be 600 and the convexity of the liabilities be 700. Suppose all bonds have a 5% yield. Then, (a) Suppose the bank wishes to hedge its equity position by going long/short in a 25-year discount bond. Find the duration based variance minimizing hedge ratio of the bank and the dollar position in the discount bond.

Question:

How do I find the duration for the 25year discount bond here?