duration

in relation to the cover assets pool or mortgage covered securities secured on the pool, means a weighted average term to maturity of the relevant principal amount of the mortgage credit assets and substitution assets comprised in the pool or those securities, as the case may be, determined in accordance with a formula or criteria specified in a regulatory notice made for the purposes of this subsection and taking into account the effect of any relevant cover assets hedge contract entered into by the institution in relation to the pool or those securities, or both, as the case may be