the as may choose one of the two options  either to pay a flat eur 080 fee per payment instruction ( option a ) or to pay a fee calculated on a degressive basis ( option b )  subject to the following modifications    for option b  the limits of the bands relating to volume of payment instructions are divided by two  and a monthly fixed fee of eur 100 ( under option a ) or eur 1 250 ( under option b ) shall be charged in addition to fixed fee i and fixed fee ii 