(1) The effect of the provisions of this chapter may be varied by agreement, to the extent the agreement does not disclaim a bank's responsibility for its own lack of good faith and is not manifestly unreasonable.
(2) Federal Reserve regulations and operating circulars, clearing-house rules, and the like have the effect of agreements under subsection (a), whether or not specifically assented to by all parties interested in items handled.
(3) Action or non-action approved by this chapter or pursuant to Federal Reserve regulations or operating circular is 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 chapter, is prima facie the exercise of ordinary care.
(4) The specification or approval of certain procedures by this chapter is not disapproval of other procedures that 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 that could not have been realized by the exercise of ordinary care. If there is also bad faith it includes any other damages the party suffered as a proximate consequence.