(1) The effect of the provisions of this Article may be varied by agreement except that no agreement can disclaim a bank's responsibility for its own lack of good faith or failure to exercise ordinary care or can limit the measure of damages for such lack or failure; but the parties may by agreement determine the standards by which such responsibility is to be measured if such standards are not manifestly unreasonable.

(2) Federal Reserve regulations and operating letters, clearing house rules, and the like, have the effect of agreements under subsection (1), whether or not specifically assented to by all parties interested in items handled.

(3) Action or non-action approved by this Article or pursuant to Federal Reserve regulations or operating letters constitutes the exercise of ordinary care and, in the absence of special instructions, action or non-action consistent with clearing house rules and the like or with a general banking usage not disapproved by this Article, prima facie constitutes the exercise of ordinary care.

(4) The specification or approval of certain procedures by this Article does not constitute disapproval of other procedures which may be reasonable under the circumstances.

(5) The measure of damages for failure to exercise ordinary care in handling an item is the amount of the item reduced by an amount which could not have been realized by the use of ordinary care, and where there is bad faith it includes other damages, if any, suffered by the party as a proximate consequence.