should liquidation and closeout under paragraph 2 of this appendix occur  the ecb shall  as soon as is reasonably practicable  take an account of what is due from each party to the other  including  as necessary  determining in respect of each transaction the ecb s total gain or loss  as the case may be  resulting from the liquidation and closeout of such transaction as at the date of such liquidation and closeout  in every case in or converted into the base currency 