(a) This code shall be liberally construed and applied to promote its underlying purposes and policies, which are:
(1) to simplify, clarify, and modernize the law governing commercial transactions;
(2) to permit the continued expansion of commercial practices through custom, usage, and agreement of the parties; and
(3) to make uniform the law among the various jurisdictions.
(b) Unless displaced by the particular provisions of this code, the principles of law and equity, including the law merchant and the law relative to capacity to contract, principal and agent, estoppel, fraud, misrepresentation, duress, coercion, mistake, bankruptcy, and other validating or invalidating cause supplement its provisions.