Solution:
The length of the potential (or revised length) is the term (or adjusted term) of the underlying contract, then the revised length of the futures contract:
=20/1.05 = 19.048 years
Currently, we will determine how many contracts (NF) to offset the loss of net value:
∆E should be equal to decline in the value of F:
∆F = -0.828 m = - MD
∆r = -19.048 * (0.382 m.)
NF* 0.005
==> NF = -0.828 / [-19.048 * (0.382 m)*0.005]
= 22.76 contracts
Therefore, in 22,76 potential contracts we also have to take a long place with the 20-year zero coupon bond as the reference.