(a) "Value." In this section, "value" has the meaning provided in section 3-303(a).
(b) Agreement not to assert claim or defense. Except as otherwise provided in this section, an agreement between an account debtor and an assignor not to assert against an assignee any claim or defense that the account debtor may have against the assignor is enforceable by an assignee that takes an assignment:
(1) For value;