Please explain and provide work on how you came to the solution. That formula I have there might be wrong.

Thanks! :)

9% 20. Al I other things equal, which of the following has the longest duration? a 20 year bond with a 1000 coupon yielding 10% a 20 year bond with a 10% coupon yielding 1100-Shor a 20 year zero coupon bond yielding 10o a 20 year zero coupon bond yielding 11% b, 21. Bond portfolio immunization techniques balance and risk. a) price; reinvestment b. price; liquidity c. credit; reinvestment d. credit; liquidity